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Gong G, Wu B, Liu L, Li J, He M. Engineering oleaginous red yeasts as versatile chassis for the production of oleochemicals and valuable compounds: Current advances and perspectives. Biotechnol Adv 2024; 76:108432. [PMID: 39163921 DOI: 10.1016/j.biotechadv.2024.108432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 07/04/2024] [Accepted: 08/16/2024] [Indexed: 08/22/2024]
Abstract
Enabling the transition towards a future circular bioeconomy based on industrial biomanufacturing necessitates the development of efficient and versatile microbial platforms for sustainable chemical and fuel production. Recently, there has been growing interest in engineering non-model microbes as superior biomanufacturing platforms due to their broad substrate range and high resistance to stress conditions. Among these non-conventional microbes, red yeasts belonging to the genus Rhodotorula have emerged as promising industrial chassis for the production of specialty chemicals such as oleochemicals, organic acids, fatty acid derivatives, terpenoids, and other valuable compounds. Advancements in genetic and metabolic engineering techniques, coupled with systems biology analysis, have significantly enhanced the production capacity of red yeasts. These developments have also expanded the range of substrates and products that can be utilized or synthesized by these yeast species. This review comprehensively examines the current efforts and recent progress made in red yeast research. It encompasses the exploration of available substrates, systems analysis using multi-omics data, establishment of genome-scale models, development of efficient molecular tools, identification of genetic elements, and engineering approaches for the production of various industrially relevant bioproducts. Furthermore, strategies to improve substrate conversion and product formation both with systematic and synthetic biology approaches are discussed, along with future directions and perspectives in improving red yeasts as more versatile biotechnological chassis in contributing to a circular bioeconomy. The review aims to provide insights and directions for further research in this rapidly evolving field. Ultimately, harnessing the capabilities of red yeasts will play a crucial role in paving the way towards next-generation sustainable bioeconomy.
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Affiliation(s)
- Guiping Gong
- Biomass Energy Technology Research Centre, Rural Energy and Ecology Research Center of CAAS, Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu 610041, PR China.
| | - Bo Wu
- Biomass Energy Technology Research Centre, Rural Energy and Ecology Research Center of CAAS, Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu 610041, PR China
| | - Linpei Liu
- Biomass Energy Technology Research Centre, Rural Energy and Ecology Research Center of CAAS, Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu 610041, PR China
| | - Jianting Li
- Biomass Energy Technology Research Centre, Rural Energy and Ecology Research Center of CAAS, Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu 610041, PR China
| | - Mingxiong He
- Biomass Energy Technology Research Centre, Rural Energy and Ecology Research Center of CAAS, Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu 610041, PR China
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Sunder S, Gupta A, Kataria R, Ruhal R. Potential of Rhodosporidium toruloides for Fatty Acids Production Using Lignocellulose Biomass. Appl Biochem Biotechnol 2024; 196:2881-2900. [PMID: 37615852 DOI: 10.1007/s12010-023-04681-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/16/2023] [Indexed: 08/25/2023]
Abstract
Microbial lipids are ideal for developing liquid biofuels because of their sustainability and no dependence on food crops. Especially the bioprocess for microbial lipids may be made economical by using sustainable approaches, e.g., lignocellulose-based carbon sources. This demand led to a search for ideal microorganisms with the ability to utilize efficiently biomass into value-added products. Rhodosporidium toruloides species belongs to the family of oleaginous (OG) yeast, which aggregates up to 70% of its biomass to produce fatty acids which can be converted to a variety of biofuels. R. toruloides is extremely adaptable to different types of feedstocks. Among all feedstock, a lot of effort is going on to develop a bioprocess of fatty acid production from lignocellulose biomass. The lignocellulose biomass is pretreated using harsh conditions of acid, alkali, and other which leads to the generation of a variety of sugars and toxic compounds. Thus, so obtained lignocellulose hydrolysate may have conditions of different pH, variable carbon and nitrogen ratios, and other non-optimum conditions. Accordingly, a detailed investigation is required for molecular level metabolism of R. toruloides in response to the hydrolysate for producing desired biochemicals like fatty acids. The present review focuses on numerous elements and obstacles, including metabolism, biofuel production, cultivation parameters, and genetic alteration of mutants in extracting fatty acids from lignocellulosic materials utilizing Rhodosporidium spp. This review provides useful information on the research working to develop processes for lignocellulose biomass using oleaginous yeast.
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Affiliation(s)
- Sushant Sunder
- Department of Biotechnology, Delhi Technological University, New Delhi, India
| | - Anshul Gupta
- Department of Biotechnology, Delhi Technological University, New Delhi, India
- Department of Physics, Technische Universität München, Munich, Germany
| | - Rashmi Kataria
- School of Bio Science and Technology, VIT Vellore, Vellore, Tamil Nadu, India.
| | - Rohit Ruhal
- School of Bio Science and Technology, VIT Vellore, Vellore, Tamil Nadu, India.
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Castañeda MT, Nuñez S, Jamilis M, De Battista H. Computational assessment of lipid production in Rhodosporidium toruloides in two-stage and one-stage batch bioprocesses. Biotechnol Bioeng 2024; 121:238-249. [PMID: 37902687 DOI: 10.1002/bit.28579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 09/04/2023] [Accepted: 10/14/2023] [Indexed: 10/31/2023]
Abstract
Oleaginous yeasts are promising platforms for microbial lipids production as a renewable and sustainable alternative to vegetable oils in biodiesel production. In this paper, a thorough in silico assessment of lipid production in batch cultivation by Rhodosporidium toruloides was developed. By means of dynamic flux balance analysis, the traditional two-stage bioprocess (TSB) performed by the native strain was contrasted with one-stage bioprocess (OSB) using four designed strains obtained by gene knockout strategies. Lipid titer, yield, content, and productivity were analyzed at different initial C/N ratios as relevant performance indicators used in bioprocesses. By weighting these indicators, a global lipid efficiency metric (GLEM) was defined to consider different scenarios. Under simulated conditions, designed strains for lipid overproduction in OSB outperformed the TSB in terms of lipid title (up to threefold), lipid yield (up to 2.4-fold), lipid content (up to 2.8-fold, with a maximum of 76%), and productivity (up to 1.3-fold), depending on C/N ratios. Using these efficiency parameters and the proposed GLEM, the process of selecting the most suitable candidates for lipid production could be carried out before experimental assays. This methodology holds the potential to be extended to other oleaginous microorganisms and diverse strain design techniques.
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Affiliation(s)
- María Teresita Castañeda
- Grupo de Control Aplicado (GCA), Instituto LEICI, UNLP-CONICET, Facultad de Ingeniería, Universidad Nacional de La Plata, La Plata, Argentina
| | - Sebastián Nuñez
- Grupo de Control Aplicado (GCA), Instituto LEICI, UNLP-CONICET, Facultad de Ingeniería, Universidad Nacional de La Plata, La Plata, Argentina
| | - Martín Jamilis
- Grupo de Control Aplicado (GCA), Instituto LEICI, UNLP-CONICET, Facultad de Ingeniería, Universidad Nacional de La Plata, La Plata, Argentina
| | - Hernán De Battista
- Grupo de Control Aplicado (GCA), Instituto LEICI, UNLP-CONICET, Facultad de Ingeniería, Universidad Nacional de La Plata, La Plata, Argentina
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Ventorim RZ, Germano VKDC, Fontes PP, da Silveira WB. Effect of carbon and nitrogen concentrations on lipid accumulation and regulation of acetyl-CoA carboxylase in Papiliotrema laurentii. Antonie Van Leeuwenhoek 2023; 116:1161-1170. [PMID: 37676572 DOI: 10.1007/s10482-023-01874-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 08/19/2023] [Indexed: 09/08/2023]
Abstract
Biodiesel is an interesting alternative to petroleum diesel as it is renewable, biodegradable, and has a low pollutant content. Yeast oils can be used for biodiesel production instead of edible oils, mitigating the use of arable land and water for biodiesel production. Maximum lipid accumulation is reached at 48 h of cultivation by the oleaginous yeast Papiliotrema laurentii UFV-1. Nevertheless, the effects of carbon and nitrogen concentrations on lipid accumulation, as well as the regulation of lipid metabolism in this yeast are still not well-characterised. Therefore, this work evaluated the effects of carbon and nitrogen concentrations on the lipid accumulation in P. laurentti, the expression of the ACC gene, and the activity of the enzyme acetyl-CoA carboxylase (ACCase) in different carbon:nitrogen ratios (C:N) and glucose concentrations. The variation of ammonium sulfate concentration did not affect the growth and lipid accumulation in P. laurentii UFV-1. On the other hand, glucose concentration remarkably influenced biomass and lipid production by this yeast. Therefore, the carbon concentration is more important than the nitrogen concentration for lipid production by P. laurentii UFV-1. Importantly, the levels of both ACC gene expression and ACCase activity were maximum during the late-exponential growth phase and decreased after reaching the highest lipid contents, which was easier evidenced during the accumulation and maximum lipid levels. As such, the reduction of ACCase enzyme activity seems to be related to the decrease in the expression level of the ACC gene.
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Optimization of Submerged Culture Parameters of the Aphid Pathogenic Fungus Fusarium equiseti Based on Sporulation and Mycelial Biomass. Microorganisms 2023; 11:microorganisms11010190. [PMID: 36677481 PMCID: PMC9865567 DOI: 10.3390/microorganisms11010190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/14/2023] Open
Abstract
Fusarium equiseti (JMF-01), as an entomopathogenic fungus, can effectively control agricultural pests and has the potential to be a biocontrol agent. To promote mycelial growth and sporulation, we investigated the optimal submerged culture conditions for F. equiseti. In this study, we used the single-factor method and Box-Behnken design and determined the virulence of the submerged culture against Myzus persicae after optimization. As a result, the highly significant factors affecting the spore concentration of strain JMF-01 were the primary inoculum density and the initial pH, and the highly significant factor affecting the mycelial biomass was the medium-to-flask ratio. The highest mycelial biomass value was 0.35 g when the incubation time was 5.68 days, the initial pH was 5.11, the medium-to-flask ratio was 0.43, and 1 mL of the primary inoculum with spore density of 0.97 × 107 conidia/mL was added. When the incubation time was 6.32 days, the initial pH was 4.46, the medium-to-flask ratio was 0.35, the primary inoculum density was 1.32 × 107 conidia/mL of 1 mL, and the highest spore concentration of 6.49 × 108 blastospores/mL was obtained. Compared with the unoptimized medium conditions, the optimized submerged culture had the highest mycelial biomass and spore concentration, which were 3.46 and 2.06 times higher, respectively. The optimized submerged culture was highly pathogenic toward M. persicae, reaching a 95% mortality rate. Our results provide optimal submerged culture conditions for F. equiseti and lay the basis for later research to expand production for pest control.
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Chen L, Peng Q, Chen Y, Wang C, Li K, Nian H. Enhancement production of lipid and unsaturation of fatty acids in Cryptococcus humicola via addition of calcium ion. World J Microbiol Biotechnol 2022; 39:50. [PMID: 36542152 DOI: 10.1007/s11274-022-03502-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
Lipids synthesized by oleaginous yeasts are considered to be the best candidates for biodiesel production. Cryptococcus humicola as an oleaginous yeast accumulated lipid in cells. In order to optimize the conditions for lipid production, different carbon and nitrogen sources were used and metals were added into the medium. Ca2+ addition increased the lipid production greatly. Xylose and peptone were optimal carbon source and nitrogen source, respectively for lipid accumulation. Response surface experiment results revealed that the accumulation of lipid could be maximized when the xylose, peptone and Ca2+ concentration was 61 g/L, 4.31 g/L, 0.67 mmol/L. C16 and C18 fatty acid account for about 91% of the total fatty acids. The most abundant fatty acid was oleic acid (42.68%), followed by palmitic acid (29.7%) and stearic acid (13.87%). The addition of Ca2+ increased the content of unsaturated fatty acids (such as C16:1 and C18:1) and improved the unsaturation of fatty acids. Quantitative real time PCR analysis revealed that expression of genes related to lipid biosynthesis showed up-regulated by Ca2+ treatment. This study provided a strategy for increase in lipid production and content of unsaturated fatty acids.
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Affiliation(s)
- Lu Chen
- Faculty of Life Science and Technology, Kunming University of Science and Technology, 650500, Kunming, China
| | - Qianyun Peng
- Faculty of Life Science and Technology, Kunming University of Science and Technology, 650500, Kunming, China
| | - Yuner Chen
- Faculty of Life Science and Technology, Kunming University of Science and Technology, 650500, Kunming, China
| | - Chengsong Wang
- Faculty of Life Science and Technology, Kunming University of Science and Technology, 650500, Kunming, China
| | - Kunzhi Li
- Faculty of Life Science and Technology, Kunming University of Science and Technology, 650500, Kunming, China
| | - Hongjuan Nian
- Faculty of Life Science and Technology, Kunming University of Science and Technology, 650500, Kunming, China.
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Optimization of agro-industrial coproducts (molasses and cassava wastewater) for the simultaneous production of lipids and carotenoids by Rhodotorula mucilaginosa. BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY 2022. [DOI: 10.1016/j.bcab.2022.102342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Mota MN, Múgica P, Sá-Correia I. Exploring Yeast Diversity to Produce Lipid-Based Biofuels from Agro-Forestry and Industrial Organic Residues. J Fungi (Basel) 2022; 8:jof8070687. [PMID: 35887443 PMCID: PMC9315891 DOI: 10.3390/jof8070687] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 06/24/2022] [Accepted: 06/27/2022] [Indexed: 12/04/2022] Open
Abstract
Exploration of yeast diversity for the sustainable production of biofuels, in particular biodiesel, is gaining momentum in recent years. However, sustainable, and economically viable bioprocesses require yeast strains exhibiting: (i) high tolerance to multiple bioprocess-related stresses, including the various chemical inhibitors present in hydrolysates from lignocellulosic biomass and residues; (ii) the ability to efficiently consume all the major carbon sources present; (iii) the capacity to produce lipids with adequate composition in high yields. More than 160 non-conventional (non-Saccharomyces) yeast species are described as oleaginous, but only a smaller group are relatively well characterised, including Lipomyces starkeyi, Yarrowia lipolytica, Rhodotorula toruloides, Rhodotorula glutinis, Cutaneotrichosporonoleaginosus and Cutaneotrichosporon cutaneum. This article provides an overview of lipid production by oleaginous yeasts focusing on yeast diversity, metabolism, and other microbiological issues related to the toxicity and tolerance to multiple challenging stresses limiting bioprocess performance. This is essential knowledge to better understand and guide the rational improvement of yeast performance either by genetic manipulation or by exploring yeast physiology and optimal process conditions. Examples gathered from the literature showing the potential of different oleaginous yeasts/process conditions to produce oils for biodiesel from agro-forestry and industrial organic residues are provided.
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Affiliation(s)
- Marta N. Mota
- iBB—Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal
- i4HB—Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal
| | - Paula Múgica
- BIOREF—Collaborative Laboratory for Biorefineries, Rua da Amieira, Apartado 1089, São Mamede de Infesta, 4465-901 Matosinhos, Portugal
| | - Isabel Sá-Correia
- iBB—Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal
- i4HB—Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal
- Correspondence:
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Gientka I, Wirkowska-Wojdyła M, Ostrowska-Ligęza E, Janowicz M, Reczek L, Synowiec A, Błażejak S. Enhancing Red Yeast Biomass Yield and Lipid Biosynthesis by Using Waste Nitrogen Source by Glucose Fed-Batch at Low Temperature. Microorganisms 2022; 10:microorganisms10061253. [PMID: 35744771 PMCID: PMC9229382 DOI: 10.3390/microorganisms10061253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 06/12/2022] [Accepted: 06/17/2022] [Indexed: 12/10/2022] Open
Abstract
This work reports the effect of simple feeding strategies and temperature to obtain high-cell-density cultures of Rhodotorula glutinis var. rubescens LOCKR13 maximizing the de novo lipid productivity using deproteinated potato wastewater (DPW) as a basic medium. Feeding DPW with glucose enables a high yield of Rhodotorula glutinis var. rubescens LOCKR13 biomass (52 g d.w. L−1) to be obtained. The highest values of lipid accumulation (34.15%, w/w), production (14.68 g L−1) and yield coefficients (YL/S: 0.242 g g−1), and volumetric productivity (PL: 0.1 g L−1 h−1) were reached by the strain in the two-stage fed-batch process at 20 °C. The lipid of yeast biomass was rich in oleic acid (Δ9C18:1) and palmitic acid (C16:0), and the lower temperature of incubation significantly increased the MUFA (especially oleic acid) content. For the first time, a unique set of thermal analyses of the microbial oil was performed. The isotherms of the oxidation kinetics (PDSC) showed that lipids extracted from the biomass of red yeast had high oxidative stability. This feature of the yeast oil can be useful for long-shelf-life food products and can be promising for the production of biodiesel.
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Affiliation(s)
- Iwona Gientka
- Department of Food Biotechnology and Microbiology, Institute of Food Science, Warsaw University of Life Sciences-SGGW, Nowoursynowska Str. 159c, 02-776 Warsaw, Poland; (A.S.); (S.B.)
- Correspondence:
| | - Magdalena Wirkowska-Wojdyła
- Department of Chemistry, Institute of Food Sciences, Warsaw University of Life Sciences-SGGW, Nowoursynowska Str. 166, 02-787 Warsaw, Poland; (M.W.-W.); (E.O.-L.)
| | - Ewa Ostrowska-Ligęza
- Department of Chemistry, Institute of Food Sciences, Warsaw University of Life Sciences-SGGW, Nowoursynowska Str. 166, 02-787 Warsaw, Poland; (M.W.-W.); (E.O.-L.)
| | - Monika Janowicz
- Department of Food Engineering and Process Management, Institute of Food Science, Warsaw University of Life Sciences-SGGW, Nowoursynowska Str. 159c, 02-776 Warsaw, Poland;
| | - Lidia Reczek
- Institute of Environmental Engineering, Warsaw University of Life Sciences–SGGW, Nowoursynowska Str. 166, 02-787 Warsaw, Poland;
| | - Alicja Synowiec
- Department of Food Biotechnology and Microbiology, Institute of Food Science, Warsaw University of Life Sciences-SGGW, Nowoursynowska Str. 159c, 02-776 Warsaw, Poland; (A.S.); (S.B.)
| | - Stanisław Błażejak
- Department of Food Biotechnology and Microbiology, Institute of Food Science, Warsaw University of Life Sciences-SGGW, Nowoursynowska Str. 159c, 02-776 Warsaw, Poland; (A.S.); (S.B.)
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Yadav AK, Kuila A, Garlapati VK. Biodiesel Production from Brassica juncea Using Oleaginous Yeast. Appl Biochem Biotechnol 2022; 194:4066-4080. [PMID: 35593952 DOI: 10.1007/s12010-022-03974-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 05/10/2022] [Indexed: 11/02/2022]
Abstract
The present study explores the potential of Brassica juncea as a low-cost substrate for biodiesel production through the growth of oleaginous yeast. Firstly, the selected lignocellulosic biomass, i.e., Brassica juncea, was thermochemically pretreated using dilute sodium hydroxide. Optimization of thermochemical pretreatment resulted in significant removal of lignin and hemicellulose with 8.4% increase in cellulose content. Further, the sugar hydrolysate of pretreated biomass was used as a substrate for the growth of selected oleaginous yeast (Cryptococcus sp. MTCC 5455). Lipid and biomass production was optimized using central composite design (CCD) based on response surface methodology (RSM). Maximum biomass and lipid content of 32.50 g/L and 11.05 g/L, respectively, was obtained at 30 °C temperature, pH 6.0, and after 5 days of incubation. The oleaginous yeast lipid was further transesterified using immobilized lipase. The highest fatty acid methyl ester 15% FAME yield was obtained after 10 h of enzymatic reaction. Next, the results of specific gravity, viscosity, flash points, and cloud point of obtained biodiesels were conformed to the ASTM D975 standard. Overall, the present study put forth the cost-effective approach for lignocellulosic biomass-based oleaginous lipid production toward the green synthesis of biodiesel.
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Affiliation(s)
- Ashok Kumar Yadav
- Department of Chemical Engineering, Banasthali Vidyapith, Banasthali, Rajasthan, 304022, India
| | - Arindam Kuila
- Department of Bioscience and Biotechnology, Banasthali Vidyapith, Banasthali, Rajasthan, 304022, India.
| | - Vijay Kumar Garlapati
- Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Himachal Pradesh, India, 173234.
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Singh S, Pandey D, Saravanabhupathy S, Daverey A, Dutta K, Arunachalam K. Liquid wastes as a renewable feedstock for yeast biodiesel production: Opportunities and challenges. ENVIRONMENTAL RESEARCH 2022; 207:112100. [PMID: 34619127 DOI: 10.1016/j.envres.2021.112100] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 09/07/2021] [Accepted: 09/19/2021] [Indexed: 06/13/2023]
Abstract
Microbial lipids (bacterial, yeast, or algal) production and its utilization as a feedstock for biodiesel production in a sustainable and economical way along with waste degradation is a promising technology. Oleaginous yeasts have demonstrated multiple advantages over algae and bacteria such as high lipid yields, lipid similarity to vegetable oil, and requirement of lesser area for cultivation. Oleaginous yeasts grown on lignocellulosic solid waste as renewable feedstocks have been widely reported and reviewed. Recently, industrial effluents and other liquid wastes have been evaluated as feedstocks for biodiesel production from oleaginous yeasts. The idea of the utilization of wastewater for the growth of oleaginous yeasts for simultaneous wastewater treatment and lipid production is gaining attention among researchers. However, the detailed knowledge on the economic aspects of different process involved during the conversion of oleaginous yeast into lipids hinders its large-scale application. Therefore, this review aims to provide an overview of yeast-derived biodiesel production by utilizing industrial effluents and other liquid wastes as feedstocks. Various technologies for biomass harvesting, lipid extraction and the economic aspects specifically focused on yeast biodiesel production were also analyzed and reported in this review. The utilization of liquid wastes and the incorporation of cost-efficient harvesting and lipid extraction strategy would facilitate large-scale commercialization of biodiesel production from oleaginous yeasts in near future.
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Affiliation(s)
- Sangeeta Singh
- National Institute of Technology Rourkela, Odisha, 769008, India
| | - Deepshikha Pandey
- School of Environment and Natural Resources, Doon University, Dehradun, 248001, India
| | | | - Achlesh Daverey
- School of Environment and Natural Resources, Doon University, Dehradun, 248001, India.
| | - Kasturi Dutta
- National Institute of Technology Rourkela, Odisha, 769008, India.
| | - Kusum Arunachalam
- School of Environment and Natural Resources, Doon University, Dehradun, 248001, India
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Evaluation of Lignocellulosic Wastewater Valorization with the Oleaginous Yeasts R. kratochvilovae EXF7516 and C. oleaginosum ATCC 20509. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation8050204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
During the conversion of lignocellulose, phenolic wastewaters are generated. Therefore, researchers have investigated wastewater valorization processes in which these pollutants are converted to chemicals, i.e., lipids. However, wastewaters are lean feedstocks, so these valorization processes in research typically require the addition of large quantities of sugars and sterilization, which increase costs. This paper investigates a repeated batch fermentation strategy with Rhodotorula kratochvilovae EXF7516 and Cutaneotrichosporon oleaginosum ATCC 20509, without these requirements. The pollutant removal and its conversion to microbial oil were evaluated. Because of the presence of non-monomeric substrates, the ligninolytic enzyme activity was also investigated. The repeated batch fermentation strategy was successful, as more lipids accumulated every cycle, up to a total of 5.4 g/L (23% cell dry weight). In addition, the yeasts consumed up to 87% of monomeric substrates, i.e., sugars, aromatics, and organics acids, and up to 23% of non-monomeric substrates, i.e., partially degraded xylan, lignin, cellulose. Interestingly, lipid production was only observed during the harvest phase of each cycle, as the cells experienced stress, possibly due to oxygen limitation. This work presents the first results on the feasibility of valorizing non-sterilized lignocellulosic wastewater with R. kratochvilovae and C. oleaginosum using a cost-effective repeated batch strategy.
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Uprety BK, Morrison EN, Emery RJN, Farrow SC. Customizing lipids from oleaginous microbes: leveraging exogenous and endogenous approaches. Trends Biotechnol 2021; 40:482-508. [PMID: 34625276 DOI: 10.1016/j.tibtech.2021.09.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/08/2021] [Accepted: 09/10/2021] [Indexed: 12/22/2022]
Abstract
To meet the growing demands of the oleochemical industry, tailored lipid sources are expanding to oleaginous microbes. To control the fatty acid composition of microbial lipids, ground-breaking exogenous and endogenous approaches are being developed. Exogenous approaches employ extracellular tools such as product-specific feedstocks, process optimization, elicitors, and magnetic and mechanical energy, whereas endogenous approaches leverage biology through the use of product-specific microbes, adaptive laboratory evolution (ALE), and the creation of custom strains via random and targeted cellular engineering. We consolidate recent advances from both fields into a review that will serve as a resource for those striving to fulfill the vision of microbial cell factories for tailored lipid production.
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Affiliation(s)
- Bijaya K Uprety
- Discovery Biology, Noblegen Inc., Peterborough, ON K9L 1Z8, Canada; Biology Department, Trent University, Peterborough, ON K9L 0G2, Canada
| | - Erin N Morrison
- Discovery Biology, Noblegen Inc., Peterborough, ON K9L 1Z8, Canada; Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON K9L 0G2, Canada
| | - R J Neil Emery
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON K9L 0G2, Canada; Biology Department, Trent University, Peterborough, ON K9L 0G2, Canada
| | - Scott C Farrow
- Discovery Biology, Noblegen Inc., Peterborough, ON K9L 1Z8, Canada; Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON K9L 0G2, Canada.
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14
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Watsuntorn W, Chuengcharoenphanich N, Niltaya P, Butkumchote C, Theerachat M, Glinwong C, Qi W, Wang Z, Chulalaksananukul W. A novel oleaginous yeast Saccharomyces cerevisiae CU-TPD4 for lipid and biodiesel production. CHEMOSPHERE 2021; 280:130782. [PMID: 34162092 DOI: 10.1016/j.chemosphere.2021.130782] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 04/22/2021] [Accepted: 04/28/2021] [Indexed: 06/08/2023]
Abstract
This study reports on the novel Saccharomyces cerevisiae CU-TPD4 that was isolated from coconut waste residues obtained from a coconut factory in Thailand. The CU-TPD4 isolate was confirmed to be a S. cerevisiae by molecular analysis and to be an oleaginous yeast with more than 20% (w/w) of the cell dry weight (CDW) present in the form of lipids. The lipid content and lipid yield of CU-TPD4 (52.96 ± 1.15% of CDW and 1.78 ± 0.06 g/L, respectively) under optimized growth conditions were much higher than those under normal growth conditions (22.65 ± 1.32% of CDW and 1.24 ± 0.12 g/L, respectively). The major fatty acids produced by CU-TPD4 were oleic (C18:1), palmitoleic (C16:1), stearic (C18:0), and palmitic (C16:0) acids. Mathematical estimation of the physical properties of the biodiesel obtained by transesterification of the extracted lipid suggested it was suitable as biodiesel with respect to the ASTM D6751 and EN 14214 international standards. Consequently, S. cerevisiae CU-TPD4 is expected to emerge as a promising alternative for biodiesel production.
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Affiliation(s)
- Wannapawn Watsuntorn
- Biofuels by Biocatalysts Research Unit, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Nuttha Chuengcharoenphanich
- Biofuels by Biocatalysts Research Unit, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Program in Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Poompat Niltaya
- Biofuels by Biocatalysts Research Unit, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Program in Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Cheryanus Butkumchote
- Biofuels by Biocatalysts Research Unit, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Program in Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Monnat Theerachat
- Biofuels by Biocatalysts Research Unit, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Chompunuch Glinwong
- Biofuels by Biocatalysts Research Unit, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Wei Qi
- Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou, 510640, China
| | - Zhongming Wang
- Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou, 510640, China
| | - Warawut Chulalaksananukul
- Biofuels by Biocatalysts Research Unit, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand.
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Production of Enriched Sporidiobolus sp. Yeast Biomass Cultivated on Mixed Coffee Hydrolyzate and Fat/Oil Waste Materials. Microorganisms 2021; 9:microorganisms9091848. [PMID: 34576745 PMCID: PMC8472217 DOI: 10.3390/microorganisms9091848] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/26/2021] [Accepted: 08/27/2021] [Indexed: 11/17/2022] Open
Abstract
One of the most addressed topics today is the transfer from a linear model of economics to a model of circular economics. It is a discipline that seeks to eliminate waste produced by various industries. The food industry generates huge amounts of waste worldwide, particularly the coffee industry, and related industries produce millions of tons of waste a year. These wastes have potential utility in biotechnology, and in the production of energy, fuels, fertilizers and nutrients, using green techniques such as anaerobic digestion, co-digestion, composting, enzymatic action, and ultrasonic and hydrothermal carbonization. This work is focused on the biotechnological use of processed spent coffee grounds (SCG) and waste fat/oil materials by some Sporidiobolus sp. carotenogenic yeasts in the model of circular economics. The results show that selected yeast strains are able to grow on SCG hydrolysate and are resistant to antimicrobial compounds present in media. The most productive strain Sporidiobolus pararoseus CCY19-9-6 was chosen for bioreactor cultivation in media with a mixture of coffee lignocellulose fraction and some fat wastes. Sporidiobolus pararoseus CCY19-9-6 was able to produce more than 22 g/L of biomass in mixture of SCG hydrolysate and both coffee oil and frying oil. The combined waste substrates induced the production of lipidic metabolites, whereby the production of carotenoids exceeded 5 mg/g of dry biomass. On media with coffee oil, this strain produced high amounts of ubiquinone (8.265 ± 1.648 mg/g) and ergosterol (13.485 ± 1.275 mg/g). Overall, the results prove that a combination of waste substrates is a promising option for the production of carotenoid- and lipid-enriched yeast biomass.
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Byrtusová D, Szotkowski M, Kurowska K, Shapaval V, Márová I. Rhodotorula kratochvilovae CCY 20-2-26-The Source of Multifunctional Metabolites. Microorganisms 2021; 9:1280. [PMID: 34208382 PMCID: PMC8231246 DOI: 10.3390/microorganisms9061280] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 06/01/2021] [Accepted: 06/08/2021] [Indexed: 01/23/2023] Open
Abstract
Multifunctional biomass is able to provide more than one valuable product, and thus, it is attractive in the field of microbial biotechnology due to its economic feasibility. Carotenogenic yeasts are effective microbial factories for the biosynthesis of a broad spectrum of biomolecules that can be used in the food and feed industry and the pharmaceutical industry, as well as a source of biofuels. In the study, we examined the effect of different nitrogen sources, carbon sources and CN ratios on the co-production of intracellular lipids, carotenoids, β-glucans and extracellular glycolipids. Yeast strain R. kratochvilovae CCY 20-2-26 was identified as the best co-producer of lipids (66.7 ± 1.5% of DCW), exoglycolipids (2.42 ± 0.08 g/L), β-glucan (11.33 ± 1.34% of DCW) and carotenoids (1.35 ± 0.11 mg/g), with a biomass content of 15.2 ± 0.8 g/L, by using the synthetic medium with potassium nitrate and mannose as a carbon source. It was shown that an increased C/N ratio positively affected the biomass yield and production of lipids and β-glucans.
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Affiliation(s)
- Dana Byrtusová
- Faculty of Science and Technology, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway; (D.B.); (V.S.)
- Faculty of Chemistry, Brno University of Technology, Purkyňova 464/118, 612 00 Brno, Czech Republic; (M.S.); (K.K.)
| | - Martin Szotkowski
- Faculty of Chemistry, Brno University of Technology, Purkyňova 464/118, 612 00 Brno, Czech Republic; (M.S.); (K.K.)
| | - Klára Kurowska
- Faculty of Chemistry, Brno University of Technology, Purkyňova 464/118, 612 00 Brno, Czech Republic; (M.S.); (K.K.)
| | - Volha Shapaval
- Faculty of Science and Technology, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway; (D.B.); (V.S.)
| | - Ivana Márová
- Faculty of Chemistry, Brno University of Technology, Purkyňova 464/118, 612 00 Brno, Czech Republic; (M.S.); (K.K.)
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Szotkowski M, Holub J, Šimanský S, Hubačová K, Sikorová P, Mariničová V, Němcová A, Márová I. Bioreactor Co-Cultivation of High Lipid and Carotenoid Producing Yeast Rhodotorula kratochvilovae and Several Microalgae under Stress. Microorganisms 2021; 9:microorganisms9061160. [PMID: 34071194 PMCID: PMC8228999 DOI: 10.3390/microorganisms9061160] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/20/2021] [Accepted: 05/25/2021] [Indexed: 11/24/2022] Open
Abstract
The co-cultivation of red yeasts and microalgae works with the idea of the natural transport of gases. The microalgae produce oxygen, which stimulates yeast growth, while CO2 produced by yeast is beneficial for algae growth. Both microorganisms can then produce lipids. The present pilot study aimed to evaluate the ability of selected microalgae and carotenogenic yeast strains to grow and metabolize in co-culture. The effect of media composition on growth and metabolic activity of red yeast strains was assessed simultaneously with microalgae mixotrophy. Cultivation was transferred from small-scale co-cultivation in Erlenmeyer flasks to aerated bottles with different inoculation ratios and, finally, to a 3L bioreactor. Among red yeasts, the strain R. kratochvilovae CCY 20-2-26 was selected because of the highest biomass production on BBM medium. Glycerol is a more suitable carbon source in the BBM medium and urea was proposed as a compromise. From the tested microalgae, Desmodesmus sp. were found as the most suitable for co-cultivations with R. kratochvilovae. In all co-cultures, linear biomass growth was found (144 h), and the yield was in the range of 8.78–11.12 g/L of dry biomass. Lipids increased to a final value of 29.62–31.61%. The FA profile was quite stable with the UFA portion at about 80%. Around 1.98–2.49 mg/g CDW of carotenoids with torularhodine as the major pigment were produced, ubiquinone production reached 5.41–6.09 mg/g, and ergosterol yield was 6.69 mg/g. Chlorophyll production was very low at 2.11 mg/g. Pilot experiments have confirmed that carotenogenic yeasts and microalgae are capable of symbiotic co-existence with a positive impact om biomass growth and lipid metabolites yields.
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Shakeri S, Khoshbasirat F, Maleki M. Rhodosporidium sp. DR37: a novel strain for production of squalene in optimized cultivation conditions. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:95. [PMID: 33858494 PMCID: PMC8048366 DOI: 10.1186/s13068-021-01947-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 04/01/2021] [Indexed: 05/06/2023]
Abstract
BACKGROUND Rhodosporidium strain, a well-known oleaginous yeast, has been widely used as a platform for lipid and carotenoid production. However, the production of squalene for application in lipid-based biofuels is not reported in this strain. Here, a new strain of Rhodosporidium sp. was isolated and identified, and its potential was investigated for production of squalene under various cultivation conditions. RESULTS In the present study, Rhodosporidium sp. DR37 was isolated from mangrove ecosystem and its potential for squalene production was assessed. When Rhodosporidium sp. DR37 was cultivated on modified YEPD medium (20 g/L glucose, 5 g/L peptone, 5 g/L YE, seawater (50% v/v), pH 7, 30 °C), 64 mg/L of squalene was produced. Also, squalene content was obtained as 13.9% of total lipid. Significantly, use of optimized medium (20 g/L sucrose, 5 g/L peptone, seawater (20% v/v), pH 7, 25 °C) allowed highest squalene accumulation (619 mg/L) and content (21.6% of total lipid) in Rhodosporidium sp. DR37. Moreover, kinetic parameters including maximum specific cell growth rate (μmax, h-1), specific lipid accumulation rate (qp, h-1), specific squalene accumulation rate (qsq, h-1) and specific sucrose consumption rate (qs, h-1) were determined in optimized medium as 0.092, 0.226, 0.036 and 0.010, respectively. CONCLUSIONS This study is the first report to employ marine oleaginous Rhodosporidium sp. DR37 for accumulation of squalene in optimized medium. These findings provide the potential of Rhodosporidium sp. DR37 for production of squalene as well as lipid and carotenoids for biofuel applications in large scale.
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Affiliation(s)
- Shahryar Shakeri
- Department of Biotechnology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran
| | - Farshad Khoshbasirat
- Department of Biotechnology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran
| | - Mahmood Maleki
- Department of Biotechnology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran
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Gosalawit C, Imsoonthornruksa S, Gilroyed BH, Mcnea L, Boontawan A, Ketudat-Cairns M. The potential of the oleaginous yeast Rhodotorula paludigena CM33 to produce biolipids. J Biotechnol 2021; 329:56-64. [PMID: 33549673 DOI: 10.1016/j.jbiotec.2021.01.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 01/04/2021] [Accepted: 01/28/2021] [Indexed: 10/22/2022]
Abstract
Sixty-seven yeast strains were isolated from castor beans then their endogenous lipids were stained by Nile Red (NR) fluorescence dye, and flow cytometry was used to obtain a strain with a high relative mean fluorescence intensity (MFI) value. The highest MFI value was obtained for strain CM33, which produced a maximum lipid content of 20.8 % dry cell weight (DCW). Based on the sequence of the ITS-5.8S-ITS rDNA and D1/D2 26S rDNA regions, CM33 showed 99 % identity with Rhodotorula paludigena. The potential of CM33 to assimilate various carbon sources was examined by growth on minimal media using glucose, glycerol, sucrose or xylose. CM33 was grown in glucose-based medium for 96 h and exhibited a maximum lipid content of 23.9 % DCW. Furthermore, when cells were cultured on molasses waste, their biomass, lipid content and lipid concentration reached 16.5 g/L, 37.1 % DCW and 6.1 g/L, respectively. These results demonstrated the potential of R. paludigena CM33 to contribute to a value-added carbon chain by converting renewable waste materials for biolipid production.
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Affiliation(s)
- Chotika Gosalawit
- School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, 111 University Avenue, Suranaree Sub-district, Muang District, Nakhon Ratchasima, 30000, Thailand.
| | - Sumeth Imsoonthornruksa
- School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, 111 University Avenue, Suranaree Sub-district, Muang District, Nakhon Ratchasima, 30000, Thailand.
| | - Brandon H Gilroyed
- School of Environmental Sciences, University of Guelph Ridgetown Campus, 120 Main Street East, Ridgetown, Ontario, N0P 2C0, Canada.
| | - Lucas Mcnea
- School of Environmental Sciences, University of Guelph Ridgetown Campus, 120 Main Street East, Ridgetown, Ontario, N0P 2C0, Canada.
| | - Apichat Boontawan
- School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, 111 University Avenue, Suranaree Sub-district, Muang District, Nakhon Ratchasima, 30000, Thailand.
| | - Mariena Ketudat-Cairns
- School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, 111 University Avenue, Suranaree Sub-district, Muang District, Nakhon Ratchasima, 30000, Thailand.
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Gao B, Wang F, Huang L, Liu H, Zhong Y, Zhang C. Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sources. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:4. [PMID: 33407769 PMCID: PMC7789750 DOI: 10.1186/s13068-020-01868-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 12/24/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND Heterotrophic cultivation of microalgae has been proposed as a viable alternative method for novel high-value biomolecules, enriched biomass, and biofuel production because of their allowance of high cell density levels, as well as simple production technology. Tetradesmus bernardii, a newly isolated high-yielding oleaginous microalga under photoautotrophic conditions, is able to grow heterotrophically, meaning that it can consume organic carbon sources in dark condition. We investigated the effect of different carbon/nitrogen (C/N) ratios on the growth and lipid accumulation of T. bernardii in heterotrophic batch culture under two nitrogen sources (NaNO3 and CO(NH2)2). In addition, we conducted time-resolved transcriptome analysis to reveal the metabolic mechanism of T. bernardii in heterotrophic culture. RESULTS T. bernardii can accumulate high biomass concentrations in heterotrophic batch culture where the highest biomass of 46.09 g/L was achieved at 100 g/L glucose concentration. The rate of glucose to biomass exceeded 55% when the glucose concentration was less than 80 g/L, and the C/N ratio was 44 at urea treatment. The culture was beneficial to lipid accumulation at a C/N ratio between 110 and 130. NaNO3 used as a nitrogen source enhanced the lipid content more than urea, and the highest lipid content was 45% of dry weight. We performed RNA-seq to analyze the time-resolved transcriptome of T. bernardii. As the nitrogen was consumed in the medium, nitrogen metabolism-related genes were significantly up-regulated to speed up the N metabolic cycle. As chloroplasts were destroyed in the dark, the metabolism of cells was transferred from chloroplasts to cytoplasm. However, storage of carbohydrate in chloroplast remained active, mainly the synthesis of starch, and the precursor of starch synthesis in heterotrophic culture may largely come from the absorption of organic carbon source (glucose). With regard to lipid metabolism, the related genes of fatty acid synthesis in low nitrogen concentration increased gradually with the extension of cultivation time. CONCLUSION T. bernardii exhibited rapid growth and high lipid accumulation in heterotrophic culture. It may be a potential candidate for biomass and biofuel production. Transcriptome analysis showed that multilevel regulation ensured the conversion from carbon to the synthesis of carbohydrate and lipid.
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Affiliation(s)
- Baoyan Gao
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China
| | - Feifei Wang
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China
| | - Luodong Huang
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China
| | - Hui Liu
- College of Resources and Environment, Zhongkai University of Agriculture and Engineering, Guangzhou, 510225, China
| | - Yuming Zhong
- College of Resources and Environment, Zhongkai University of Agriculture and Engineering, Guangzhou, 510225, China
| | - Chengwu Zhang
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China.
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Vieira NM, Dos Santos RCV, Germano VKDC, Ventorim RZ, de Almeida ELM, da Silveira FA, Ribeiro Júnior JI, da Silveira WB. Isolation of a new Papiliotrema laurentii strain that displays capacity to achieve high lipid content from xylose. 3 Biotech 2020; 10:382. [PMID: 32802724 DOI: 10.1007/s13205-020-02373-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 07/31/2020] [Indexed: 02/06/2023] Open
Abstract
In this work, we isolated and selected oleaginous yeasts from rock field soils from two National Parks in Brazil (Caparaó and Serra dos Órgãos) with the potential to accumulate oil from xylose, the main pentose sugar found in lignocellulosic biomass. From the 126 isolates, two were selected based on their lipid contents. They were taxonomically identified as Papiliotrema laurentii (UFV-1 and UFV-2). Of the two, P. laurentii UFV-1 was selected as the best lipid producer. Under unoptimized conditions, lipid production by P. laurentii UFV-1 was higher in glucose than in xylose. To improve its lipid production from xylose, we applied response surface methodology (RSM) with a face-centered central composite design (CCF). We evaluated the effects of agitation rate, initial cell biomass (OD600), carbon/nitrogen ratio (C/N ratio) and pH on lipid production. P. laurentii UFV-1 recorded the highest lipid content, 63.5% (w/w) of the cell dry mass, under the following conditions: C/N ratio = 100:1, pH value = 7.0, initial OD600 = 0.8 and agitation = 300 rpm. Under these optimized conditions, biomass, lipid titer and volumetric lipid productivity were 9.31 g/L, 5.90 g/L and 0.082 g/L.h, respectively. Additionally, we determined the fatty acid composition of P. laurentii UFV-1 as follows: C14:0 (0.5%), C16:0 (28.4-29.4%), C16:1 (0.2%), C18:0 (9.5-11%), C18:1 (58.6-60.5%), and C20:0 (0.7-0.8%). Based on this composition, the predicted properties of biodiesel showed that P. laurentii UFV-1 oil is suitable for use as feedstock in biodiesel production.
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Affiliation(s)
- Nívea Moreira Vieira
- Laboratory of Microbial Physiology, Department of Microbiology, Federal University of Viçosa, Av. P. H. Rolfs, s/n, Viçosa, MG 36570-900 Brazil
| | - Raquel Cristina Vieira Dos Santos
- Laboratory of Microbial Physiology, Department of Microbiology, Federal University of Viçosa, Av. P. H. Rolfs, s/n, Viçosa, MG 36570-900 Brazil
| | - Vanessa Kely de Castro Germano
- Laboratory of Microbial Physiology, Department of Microbiology, Federal University of Viçosa, Av. P. H. Rolfs, s/n, Viçosa, MG 36570-900 Brazil
| | - Rafaela Zandonade Ventorim
- Laboratory of Microbial Physiology, Department of Microbiology, Federal University of Viçosa, Av. P. H. Rolfs, s/n, Viçosa, MG 36570-900 Brazil
| | - Eduardo Luís Menezes de Almeida
- Laboratory of Microbial Physiology, Department of Microbiology, Federal University of Viçosa, Av. P. H. Rolfs, s/n, Viçosa, MG 36570-900 Brazil
| | - Fernando Augusto da Silveira
- Laboratory of Microbial Physiology, Department of Microbiology, Federal University of Viçosa, Av. P. H. Rolfs, s/n, Viçosa, MG 36570-900 Brazil
| | | | - Wendel Batista da Silveira
- Laboratory of Microbial Physiology, Department of Microbiology, Federal University of Viçosa, Av. P. H. Rolfs, s/n, Viçosa, MG 36570-900 Brazil
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Diwan B, Gupta P. A Deuteromycete Isolate Geotrichum candidum as Oleaginous Cell Factory for Medium-Chain Fatty Acid-Rich Oils. Curr Microbiol 2020; 77:3738-3749. [PMID: 32778944 DOI: 10.1007/s00284-020-02155-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 07/29/2020] [Indexed: 10/23/2022]
Abstract
Single cell oils (SCO) are oils derived from microorganisms which have potential to hyperaccumulate intracellular lipids (called oleaginous) under some essential nutrient (nitrogen, phosphorous or sometimes sulphur) starvation and an excess of carbon. The present work investigates the influence of these key parameters (for triggering oleaginicity), i.e. carbon (C) and nitrogen (N) on oleaginous behaviour of an oleaginous isolate, with the objective of improving the lipid content and obtaining oils of applicative interest. Eleven yeasts were isolated from rotten fruits and a unique yeast from rotten apple was screened on the basis of its ~ 20% (of dry mass) lipid content (LC), trademark of oleaginicity under nitrogen-stressed culture conditions. Subsequent investigation on influence of C, N and w/w ratio of carbon source concentration (Cs) to nitrogen source concentration (Ns) was conducted on this isolate. The isolate was identified as a Deuteromycete-Geotrichum candidum. 4.8 g/l was found to be minimum N concentration and glucose as suitable C source for optimum balance between biomass and lipid content. The highest LC of 73.6% (172.5% higher compared to 27% LC at Cs/Ns 80/4.8) was obtained at Cs/Ns 150/4.8 with a lipid coefficient of 8.7 (g lipid/100 g substrate). While remarkably higher production economy (lipid coefficient of 28.45) was noted at Cs/Ns 100/4.8 with significant LC of 54.4% (~ 100% higher than at Cs/Ns 80/4.8). The derived oils were predominantly rich in medium-chain fatty acids (MCFA)-caprylic acid, rare in plant oils. G. candidum is a previously referred oleaginous species; however, for the first time this study illustrates its detailed oleaginous behaviour and lipid compositional characteristics with varying nutritional parameters. The work is a progressive contribution towards current and upcoming researches in field of SCOs. Compositional characteristics of derived oils, make it an important candidate for potential medical and nutritional applications in future.
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Affiliation(s)
- Batul Diwan
- Department of Biotechnology, National Institute of Technology, Raipur, India
| | - Pratima Gupta
- Department of Biotechnology, National Institute of Technology, Raipur, India.
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Radha P, Prabhu K, Jayakumar A, AbilashKarthik S, Ramani K. Biochemical and kinetic evaluation of lipase and biosurfactant assisted ex novo synthesis of microbial oil for biodiesel production by Yarrowia lipolytica utilizing chicken tallow. Process Biochem 2020. [DOI: 10.1016/j.procbio.2020.05.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Revealing the Potential of Lipid and β-Glucans Coproduction in Basidiomycetes Yeast. Microorganisms 2020; 8:microorganisms8071034. [PMID: 32668638 PMCID: PMC7409317 DOI: 10.3390/microorganisms8071034] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/07/2020] [Accepted: 07/08/2020] [Indexed: 12/28/2022] Open
Abstract
Beta (β)-glucans are polysaccharides composed of D-glucose monomers. Nowadays, β-glucans are gaining attention due to their attractive immunomodulatory biological activities, which can be utilized in pharmaceutical or food supplementation industries. Some carotenogenic Basidiomycetes yeasts, previously explored for lipid and carotenoid coproduction, could potentially coproduce a significant amount of β-glucans. In the present study, we screened eleven Basidiomycetes for the coproduction of lipids and β-glucans. We examined the effect of four different C/N ratios and eight different osmolarity conditions on the coproduction of lipids and β-glucans. A high-throughput screening approach employing microcultivation in microtiter plates, Fourier Transform Infrared (FTIR) spectroscopy and reference analysis was utilized in the study. Yeast strains C. infirmominiatum CCY 17-18-4 and R. kratochvilovae CCY 20-2-26 were identified as the best coproducers of lipids and β-glucans. In addition, C. infirmominiatum CCY 17-18-4, R. kratochvilovae CCY 20-2-26 and P. rhodozyma CCY 77-1-1 were identified as the best alternative producers of β-glucans. Increased C/N ratio led to increased biomass, lipid and β-glucans production for several yeast strains. Increased osmolarity had a negative effect on biomass and lipid production while the β-glucan production was positively affected.
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Altun R, Esim N, Aykutoglu G, Baltaci MO, Adiguzel A, Taskin M. Production of linoleic acid‐rich lipids in molasses‐based medium by oleaginous fungus
Galactomyces geotrichum
TS61. J FOOD PROCESS PRES 2020. [DOI: 10.1111/jfpp.14518] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Ramazan Altun
- Department of Molecular Biology and Genetics Science Faculty Ataturk University Erzurum Turkey
| | - Nevzat Esim
- Department of Molecular Biology and Genetics Science Faculty Bingol University Bingol Turkey
| | - Gurkan Aykutoglu
- Department of Molecular Biology and Genetics Science Faculty Bingol University Bingol Turkey
| | - Mustafa Ozkan Baltaci
- Department of Molecular Biology and Genetics Science Faculty Ataturk University Erzurum Turkey
| | - Ahmet Adiguzel
- Department of Molecular Biology and Genetics Science Faculty Ataturk University Erzurum Turkey
| | - Mesut Taskin
- Department of Molecular Biology and Genetics Science Faculty Ataturk University Erzurum Turkey
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Lipid Production from Sugarcane Top Hydrolysate and Crude Glycerol with Rhodosporidiobolus fluvialis using a Two-Stage Batch-Cultivation Strategy with Separate Optimization of Each Stage. Microorganisms 2020; 8:microorganisms8030453. [PMID: 32210119 PMCID: PMC7143989 DOI: 10.3390/microorganisms8030453] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 03/19/2020] [Accepted: 03/21/2020] [Indexed: 11/23/2022] Open
Abstract
Lipids from oleaginous microorganisms, including oleaginous yeasts, are recognized as feedstock for biodiesel production. A production process development of these organisms is necessary to bring lipid feedstock production up to the industrial scale. This study aimed to enhance lipid production of low-cost substrates, namely sugarcane top and biodiesel-derived crude glycerol, by using a two-stage cultivation process with Rhodosporidiobolus fluvialis DMKU-SP314. In the first stage, sugarcane top hydrolysate was used for cell propagation, and in the second stage, cells were suspended in a crude glycerol solution for lipid production. Optimization for high cell mass production in the first stage, and for high lipid production in the second stage, were performed separately using a one-factor-at-a-time methodology together with response surface methodology. Under optimum conditions in the first stage (sugarcane top hydrolysate broth containing; 43.18 g/L total reducing sugars, 2.58 g/L soy bean powder, 0.94 g/L (NH4)2SO4, 0.39 g/L KH2PO4 and 2.5 g/L MgSO4 7H2O, pH 6, 200 rpm, 28 °C and 48 h) and second stage (81.54 g/L crude glycerol, pH 5, 180 rpm, 27 °C and 196 h), a high lipid concentration of 15.85 g/L, a high cell mass of 21.07 g/L and a high lipid content of 73.04% dry cell mass were obtained.
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Study of Metabolic Adaptation of Red Yeasts to Waste Animal Fat Substrate. Microorganisms 2019; 7:microorganisms7110578. [PMID: 31752339 PMCID: PMC6920810 DOI: 10.3390/microorganisms7110578] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 11/10/2019] [Accepted: 11/14/2019] [Indexed: 02/05/2023] Open
Abstract
Carotenogenic yeasts are non-conventional oleaginous microorganisms capable of utilizing various waste substrates. In this work, four red yeast strains (Rhodotorula, Cystofilobasidium, and Sporobolomyces sp.) were cultivated in media containing crude, emulsified, and enzymatically hydrolyzed animal waste fat, compared with glucose and glycerol, as single C-sources. Cell morphology (cryo-SEM (cryo-scanning electron microscopy), TEM (transmission electron microscopy)), production of biomass, lipase, biosurfactants, lipids (gas chromatography/flame ionization detection, GC/FID) carotenoids, ubiquinone, and ergosterol (high performance liquid chromatography, HPLC/PDA) in yeast cells was studied depending on the medium composition, the C source, and the carbon/nitrogen (C/N) ratio. All studied strains are able to utilize solid and processed fat. Biomass production at C/N = 13 was higher on emulsified/hydrolyzed fat than on glucose/glycerol. The production of lipids and lipidic metabolites was enhanced for several times on fat; the highest yields of carotenoids (24.8 mg/L) and lipids (54.5%/CDW (cell dry weight)) were found in S. pararoseus. Simultaneous induction of lipase and biosurfactants was observed on crude fat substrate. An increased C/N ratio (13-100) led to higher biomass production in fat media. The production of total lipids increased in all strains to C/N = 50. Oppositely, the production of carotenoids, ubiquinone, and ergosterol dramatically decreased with increased C/N in all strains. Compounds accumulated in stressed red yeasts have a great application potential and can be produced efficiently during the valorization of animal waste fat under the biorefinery concept.
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Lipid and Carotenoid Production by Rhodotorula glutinis with a Combined Cultivation Mode of Nitrogen, Sulfur, and Aluminium Stress. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9122444] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Torulene is a promising pink pigment, produced only by yeasts and fungi, and its production is still in a developing stage due to the low production rate. Accordingly, this study focuses on maximizing torulene production by Rhodotorula glutinis using shaken flask fermentation. The effect of different nitrogen sources, and C/N and C/S ratios on lipid and carotenoid production by R. glutinis was studied using 60 g/L glucose. The largest cells filled with golden fluorescence lipid bodies were observed using fluorescence microscopy when peptone was used as a nitrogen source. The highest total pigment (0.947 mg/L) and carotenoid relative productivity (Car-RP) (89.04 µg/g) were obtained at C/N 146 and C/S 120, and with ammonium sulfate as a nitrogen source, with 62% torulene domination using High Performance Liquid Chromatography (HPLC) for identification. Under a high C/N ratio, regardless of the C/S ratio, the carotenoid synthesis rate decreased after three days while the lipid synthesis rate kept increasing to the sixth day. Interestingly, after adding 0.7 mM Al2(SO4)3 to the optimized medium, the total pigment and Car-RP (2.2 mg/L and 212.9 µg/g) sharply increased, producing around 2.16 mg/L torulene (98%) with around 50% decrease in lipid yield. This is the first report on the role of Al2(SO4)3 for enhancing torulene production under lipogenesis condition, which could be used as a potential tool for torulene production.
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Kot AM, Błażejak S, Kieliszek M, Gientka I, Bryś J. Simultaneous Production of Lipids and Carotenoids by the Red Yeast Rhodotorula from Waste Glycerol Fraction and Potato Wastewater. Appl Biochem Biotechnol 2019; 189:589-607. [PMID: 31073981 PMCID: PMC6754821 DOI: 10.1007/s12010-019-03023-z] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Accepted: 04/22/2019] [Indexed: 02/04/2023]
Abstract
Abstract The objective of this study was to determine the possibility of simultaneous biosynthesis of lipids and carotenoids by the Rhodotorula yeast strains in media with waste glycerol and deproteinized potato wastewater and to determine the level of pollution reduction by media. On the basis of results obtained during the yeast microcultures in the Bioscreen C system, it was found that potato wastewater and glycerol can be used as components of media for Rhodotorula glutinis, Rhodotorula mucilaginosa, and Rhodotorula gracilis yeast strains. The amount of glycerol added to media higher than 10% significantly decreased the growth rate of yeast. The results of yeast culture in the laboratory shaker flasks showed a possibility of simultaneous production of lipids and carotenoids by R. glutinis, R. mucilaginosa, and R. gracilis yeast strains during cultivation in media containing only waste glycerol and deproteinized potato wastewater. A higher intracellular lipid content (approximately 15 g/100 gd.w.) was obtained for R. mucilaginosa and R. gracilis yeast biomass after cultivation in experimental media with waste glycerol and potato wastewater. In conclusion, the yeast grown in media with potato wastewater supplemented with 3% or 5% glycerol synthesized carotenoids, and their content in biomass did not exceed 230 μg/gd.w.
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Affiliation(s)
- Anna M Kot
- Department of Biotechnology, Microbiology and Food Evaluation, Faculty of Food Sciences, Warsaw University of Life Sciences, ul. Nowoursynowska 159C, 02-776, Warszawa, Poland.
| | - Stanisław Błażejak
- Department of Biotechnology, Microbiology and Food Evaluation, Faculty of Food Sciences, Warsaw University of Life Sciences, ul. Nowoursynowska 159C, 02-776, Warszawa, Poland
| | - Marek Kieliszek
- Department of Biotechnology, Microbiology and Food Evaluation, Faculty of Food Sciences, Warsaw University of Life Sciences, ul. Nowoursynowska 159C, 02-776, Warszawa, Poland
| | - Iwona Gientka
- Department of Biotechnology, Microbiology and Food Evaluation, Faculty of Food Sciences, Warsaw University of Life Sciences, ul. Nowoursynowska 159C, 02-776, Warszawa, Poland
| | - Joanna Bryś
- Department of Chemistry, Faculty of Food Sciences, Warsaw University of Life Sciences, ul. Nowoursynowska 159C, 02-776, Warszawa, Poland
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Jiru TM, Steyn L, Pohl C, Abate D. Production of single cell oil from cane molasses by Rhodotorula kratochvilovae (syn, Rhodosporidium kratochvilovae) SY89 as a biodiesel feedstock. Chem Cent J 2018; 12:91. [PMID: 30097852 PMCID: PMC6086781 DOI: 10.1186/s13065-018-0457-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 07/31/2018] [Indexed: 12/04/2022] Open
Abstract
Background Single cell oil has long been considered an alternative to conventional oil sources. The oil produced can also be used as a feedstock for biodiesel production. Oleaginous yeasts have relatively high growth and lipid production rates, can utilize a wide variety of cheap agro-industrial wastes such as molasses, and can accumulate lipids above 20% of their biomass when they are grown in a bioreactor under conditions of controlled excess carbon and nitrogen limitation. Results In this study, Rhodotorula kratochvilovae (syn, Rhodosporidium kratochvilovae) SY89 was cultivated in a nitrogen-limited medium containing cane molasses as a carbon source. The study aims to provide not only information on the production of single cell oil using R. kratochvilovae SY89 on cane molasses as a biodiesel feedstock, but also to characterize the biodiesel obtained from the resultant lipids. After determination of the sugar content in cane molasses, R. kratochvilovae SY89 was grown on the optimized cane molasses for 168 h. Under the optimized conditions, the yeast accumulated lipids up to 38.25 ± 1.10% on a cellular dry biomass basis. This amount corresponds to a lipid yield of 4.82 ± 0.27 g/L. The fatty acid profiles of the extracted yeast lipids were analyzed using gas chromatography, coupled with flame ionization detector. A significant amount of oleic acid (58.51 ± 0.76%), palmitic acid (15.70 ± 1.27%), linoleic acid (13.29 ± 1.18%) and low amount of other fatty acids were detected in the extracted yeast lipids. The lipids were used to prepare biodiesel and the yield was 85.30%. The properties of this biodiesel were determined and found to be comparable to the specifications established by ASTM D6751 and EN14214 related to biodiesel quality. Conclusions Based on the results obtained, the biodiesel from R. kratochvilovae SY89 oil could be a competitive alternative to conventional diesel fuel.
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Affiliation(s)
- Tamene Milkessa Jiru
- Department of Biotechnology, University of Gondar, P.O.Box: 196, Gondar, Ethiopia.
| | - Laurinda Steyn
- Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, P.O.Box: 339, Bloemfontein, South Africa
| | - Carolina Pohl
- Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, P.O.Box: 339, Bloemfontein, South Africa
| | - Dawit Abate
- Microbial, Cellular and Molecular Biology Department, College of Natural Sciences, Addis Ababa University, P.O.Box: 1176, Addis Ababa, Ethiopia
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