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Zhang MY, Xu XR, Zhao RP, Huang C, Song YD, Zhao ZT, Zhao YB, Ren XJ, Zhao XH. Mechanism of enhanced microalgal biomass and lipid accumulation through symbiosis between a highly succinic acid-producing strain of Escherichia coli SUC and Aurantiochytrium sp. SW1. BIORESOURCE TECHNOLOGY 2024; 394:130232. [PMID: 38141881 DOI: 10.1016/j.biortech.2023.130232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 12/19/2023] [Accepted: 12/19/2023] [Indexed: 12/25/2023]
Abstract
Microalgae, known for rapid growth and lipid richness, hold potential in biofuels and high-value biomolecules. The symbiotic link with bacteria is crucial in large-scale open cultures. This study explores algal-bacterial interactions using a symbiotic model, evaluating acid-resistant Lactic acid bacteria (LAB), stress-resilient Bacillus subtilis and Bacillus licheniformis, and various Escherichia coli strains in the Aurantiochytrium sp. SW1 system. It was observed that E. coli SUC significantly enhanced the growth and lipid production of Aurantiochytrium sp. SW1 by increasing enzyme activity (NAD-IDH, NAD-ME, G6PDH) while maintaining sustained succinic acid release. Optimal co-culture conditions included temperature 28 °C, a 1:10 algae-to-bacteria ratio, and pH 8. Under these conditions, Aurantiochytrium sp. SW1 biomass increased 3.17-fold to 27.83 g/L, and total lipid content increased 2.63-fold to 4.87 g/L. These findings have implications for more efficient microalgal lipid production and large-scale cultivation.
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Affiliation(s)
- Mei-Yu Zhang
- International Cooperative Joint Laboratory for Marine Microbial Cell Factories, Colin Ratledge Center for Microbial Lipids, College of Agricultural Engineering and Food Science, Shandong University of Technology, China; Shandong (Zibo) Prefabricated Food Research Center, College of Agricultural Engineering and Food Science, Shandong University of Technology, Shandong, China
| | - Xin-Ru Xu
- International Cooperative Joint Laboratory for Marine Microbial Cell Factories, Colin Ratledge Center for Microbial Lipids, College of Agricultural Engineering and Food Science, Shandong University of Technology, China
| | - Ru-Ping Zhao
- International Cooperative Joint Laboratory for Marine Microbial Cell Factories, Colin Ratledge Center for Microbial Lipids, College of Agricultural Engineering and Food Science, Shandong University of Technology, China
| | - Chao Huang
- International Cooperative Joint Laboratory for Marine Microbial Cell Factories, Colin Ratledge Center for Microbial Lipids, College of Agricultural Engineering and Food Science, Shandong University of Technology, China
| | - Yuan-Da Song
- International Cooperative Joint Laboratory for Marine Microbial Cell Factories, Colin Ratledge Center for Microbial Lipids, College of Agricultural Engineering and Food Science, Shandong University of Technology, China
| | - Zi-Tong Zhao
- Shandong (Zibo) Prefabricated Food Research Center, College of Agricultural Engineering and Food Science, Shandong University of Technology, Shandong, China
| | - Yu-Bin Zhao
- Luzhou Bio-Chem Technology Limited, Linyi, China
| | - Xiao-Jie Ren
- International Cooperative Joint Laboratory for Marine Microbial Cell Factories, Colin Ratledge Center for Microbial Lipids, College of Agricultural Engineering and Food Science, Shandong University of Technology, China; Shandong (Zibo) Prefabricated Food Research Center, College of Agricultural Engineering and Food Science, Shandong University of Technology, Shandong, China.
| | - Xin-He Zhao
- International Cooperative Joint Laboratory for Marine Microbial Cell Factories, Colin Ratledge Center for Microbial Lipids, College of Agricultural Engineering and Food Science, Shandong University of Technology, China; Shandong (Zibo) Prefabricated Food Research Center, College of Agricultural Engineering and Food Science, Shandong University of Technology, Shandong, China; Shanli Health Food Technology Co., LTD, Shandong, China.
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Engineering Microorganisms to Produce Bio-Based Monomers: Progress and Challenges. FERMENTATION-BASEL 2023. [DOI: 10.3390/fermentation9020137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Bioplastics are polymers made from sustainable bio-based feedstocks. While the potential of producing bio-based monomers in microbes has been investigated for decades, their economic feasibility is still unsatisfactory compared with petroleum-derived methods. To improve the overall synthetic efficiency of microbial cell factories, three main strategies were summarized in this review: firstly, implementing approaches to improve the microbial utilization ability of cheap and abundant substrates; secondly, developing methods at enzymes, pathway, and cellular levels to enhance microbial production performance; thirdly, building technologies to enhance microbial pH, osmotic, and metabolites stress tolerance. Moreover, the challenges of, and some perspectives on, exploiting microorganisms as efficient cell factories for producing bio-based monomers are also discussed.
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Zhou S, Zhang M, Zhu L, Zhao X, Chen J, Chen W, Chang C. Hydrolysis of lignocellulose to succinic acid: a review of treatment methods and succinic acid applications. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:1. [PMID: 36593503 PMCID: PMC9806916 DOI: 10.1186/s13068-022-02244-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 12/08/2022] [Indexed: 01/03/2023]
Abstract
Succinic acid (SA) is an intermediate product of the tricarboxylic acid cycle (TCA) and is one of the most significant platform chemicals for the production of various derivatives with high added value. Due to the depletion of fossil raw materials and the demand for eco-friendly energy sources, SA biosynthesis from renewable energy sources is gaining attention for its environmental friendliness. This review comprehensively analyzes strategies for the bioconversion of lignocellulose to SA based on the lignocellulose pretreatment processes and cellulose hydrolysis and fermentation principles and highlights the research progress on acid production and SA utilization under different microbial culture conditions. In addition, the fermentation efficiency of different microbial strains for the production of SA and the main challenges were analyzed. The future application directions of SA derivatives were pointed out. It is expected that this research will provide a reference for the optimization of SA production from lignocellulose.
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Affiliation(s)
- Shuzhen Zhou
- College of Chemical Engineering, Zhengzhou University, Zhengzhou, China
| | - Miaomiao Zhang
- College of Chemical Engineering, Zhengzhou University, Zhengzhou, China
| | - Linying Zhu
- College of Management Engineering, Zhengzhou University, Zhengzhou, China
| | - Xiaoling Zhao
- College of Chemical Engineering, Zhengzhou University, Zhengzhou, China.
- State Key Laboratory of Motor Vehicle Biofuel Technology, Nanyang, China.
- Henan Center for Outstanding Overseas Scientists, Zhengzhou, China.
| | - Junying Chen
- College of Chemical Engineering, Zhengzhou University, Zhengzhou, China
- State Key Laboratory of Motor Vehicle Biofuel Technology, Nanyang, China
- Henan Center for Outstanding Overseas Scientists, Zhengzhou, China
| | - Wei Chen
- Henan Key Laboratory of Green Manufacturing of Biobased Chemicals, Puyang, China
| | - Chun Chang
- College of Chemical Engineering, Zhengzhou University, Zhengzhou, China
- State Key Laboratory of Motor Vehicle Biofuel Technology, Nanyang, China
- Henan Center for Outstanding Overseas Scientists, Zhengzhou, China
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Yu C, Wang HP, Qiao T, Zhao Y, Yu X. A fed-batch feeding with succinic acid strategy for astaxanthin and lipid hyper-production in Haematococcus pluviualis. BIORESOURCE TECHNOLOGY 2021; 340:125648. [PMID: 34332443 DOI: 10.1016/j.biortech.2021.125648] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/19/2021] [Accepted: 07/20/2021] [Indexed: 06/13/2023]
Abstract
Effects of succinic acid (SA) in fed-batch feeding mode on astaxanthin and lipids biopoduction of Haematococcus pluvialis against abiotic stresses were explored. By comparison with the control, the initial addition of SA on day 0 increased the production of astaxanthin by 71.61%. More importantly, the maximum values of astaxanthin (35.88 mg g-1) and lipid (54.79%) contents were obtained after supplementation of SA on day 7. Meanwhile, under SA treatment, the chlorophyll, carbohydrate, and protein levels were reduced, but the intracellular levels of SA and reactive oxygen species (ROS), the transcription levels of astaxanthin and fatty acids biosynthesis-, and antioxidant system-related genes were increased. Furthermore, scaling-up cultivation in bioreactor further enhanced the astaxanthin productivity from H. pluvialis. Generally, this study proved the intermittent SA feeding method in fed-batch culture as a potent strategy that facilitated massive astaxanthin and lipids production in algae.
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Affiliation(s)
- Chunli Yu
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, China
| | - Hui-Ping Wang
- Children's Hospital Affiliated to Kunming Medical University, Kunming 650228, China
| | - Tengsheng Qiao
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, China
| | - Yongteng Zhao
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, China
| | - Xuya Yu
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, China.
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Lv Z, Zhou J, Zhang Y, Zhou X, Xu N, Xin F, Ma J, Jiang M, Dong W. Techniques for enhancing the tolerance of industrial microbes to abiotic stresses: A review. Biotechnol Appl Biochem 2019; 67:73-81. [PMID: 31206805 DOI: 10.1002/bab.1794] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 06/05/2019] [Indexed: 12/20/2022]
Abstract
The diversity of stress responses and survival strategies evolved by microorganism enables them to survive and reproduce in a multitude of harsh environments, whereas the discovery of the underlying resistance genes or mechanisms laid the foundation for the directional enhancement of microbial tolerance to abiotic stresses encountered in industrial applications. Many biological techniques have been developed for improving the stress resistance of industrial microorganisms, which greatly benefited the bacteria on which industrial production is based. This review introduces the main techniques for enhancing the resistance of microorganisms to abiotic stresses, including evolutionary engineering, metabolic engineering, and process engineering, developed in recent years. In addition, we also discuss problems that are still present in this area and offer directions for future research.
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Affiliation(s)
- Ziyao Lv
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
| | - Jie Zhou
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China.,Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
| | - Yue Zhang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
| | - Xinhai Zhou
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
| | - Ning Xu
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
| | - Fengxue Xin
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China.,Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
| | - Jiangfeng Ma
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China.,Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
| | - Min Jiang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China.,Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
| | - Weiliang Dong
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China.,Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, 211800, Peoples' Republic of China
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Exploring cellular fatty acid composition and intracellular metabolites of osmotic-tolerant mutant Lactobacillus paracasei NCBIO-M2 for highly efficient lactic acid production with high initial glucose concentration. J Biotechnol 2018; 286:27-35. [DOI: 10.1016/j.jbiotec.2018.09.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 08/27/2018] [Accepted: 09/11/2018] [Indexed: 11/22/2022]
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7
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Guo S, Yi X, Zhang W, Wu M, Xin F, Dong W, Zhang M, Ma J, Wu H, Jiang M. Inducing hyperosmotic stress resistance in succinate-producing Escherichia coli by using the response regulator DR1558 from Deinococcus radiodurans. Process Biochem 2017. [DOI: 10.1016/j.procbio.2017.06.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Osmotolerance in Escherichia coli Is Improved by Activation of Copper Efflux Genes or Supplementation with Sulfur-Containing Amino Acids. Appl Environ Microbiol 2017; 83:AEM.03050-16. [PMID: 28115377 DOI: 10.1128/aem.03050-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 01/09/2017] [Indexed: 11/20/2022] Open
Abstract
Improvement in the osmotolerance of Escherichia coli is essential for the production of high titers of various bioproducts. In this work, a cusS mutation that was identified in the previously constructed high-succinate-producing E. coli strain HX024 was investigated for its effect on osmotolerance. CusS is part of the two-component system CusSR that protects cells from Ag(I) and Cu(I) toxicity. Changing cusS from strain HX024 back to its original sequence led to a 24% decrease in cell mass and succinate titer under osmotic stress (12% glucose). When cultivated with a high initial glucose concentration (12%), introduction of the cusS mutation into parental strain Suc-T110 led to a 21% increase in cell mass and a 40% increase in succinate titer. When the medium was supplemented with 30 g/liter disodium succinate, the cusS mutation led to a 120% increase in cell mass and a 492% increase in succinate titer. Introducing the cusS mutation into the wild-type strain ATCC 8739 led to increases in cell mass of 87% with 20% glucose and 36% using 30 g/liter disodium succinate. The cusS mutation increased the expression of cusCFBA, and gene expression levels were found to be positively related to osmotolerance abilities. Because high osmotic stress has been associated with deleterious accumulation of Cu(I) in the periplasm, activation of CusCFBA may alleviate this effect by transporting Cu(I) out of the cells. This hypothesis was confirmed by supplementing sulfur-containing amino acids that can chelate Cu(I). Adding methionine or cysteine to the medium increased the osmotolerance of E. coli under anaerobic conditions.IMPORTANCE In this work, an activating Cus copper efflux system was found to increase the osmotolerance of E. coli In addition, new osmoprotectants were identified. Supplementation with methionine or cysteine led to an increase in osmotolerance of E. coli under anaerobic conditions. These new strategies for improving osmotolerance will be useful for improving the production of chemicals in industrial bioprocesses.
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Xiao M, Zhu X, Xu H, Tang J, Liu R, Bi C, Fan F, Zhang X. A novel point mutation in RpoB improves osmotolerance and succinic acid production in Escherichia coli. BMC Biotechnol 2017; 17:10. [PMID: 28193207 PMCID: PMC5307762 DOI: 10.1186/s12896-017-0337-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 02/10/2017] [Indexed: 11/29/2022] Open
Abstract
Background Escherichia coli suffer from osmotic stress during succinic acid (SA) production, which reduces the performance of this microbial factory. Results Here, we report that a point mutation leading to a single amino acid change (D654Y) within the β-subunit of DNA-dependent RNA polymerase (RpoB) significantly improved the osmotolerance of E. coli. Importation of the D654Y mutation of RpoB into the parental strain, Suc-T110, increased cell growth and SA production by more than 40% compared to that of the control under high glucose osmolality. The transcriptome profile, determined by RNA-sequencing, showed two distinct stress responses elicited by the mutated RpoB that counterbalanced the osmotic stress. Under non-stressed conditions, genes involved in the synthesis and transport of compatible solutes such as glycine-betaine, glutamate or proline were upregulated even without osmotic stimulation, suggesting a “pre-defense” mechanism maybe formed in the rpoB mutant. Under osmotic stressed conditions, genes encoding diverse sugar transporters, which should be down-regulated in the presence of high osmotic pressure, were derepressed in the rpoB mutant. Additional genetic experiments showed that enhancing the expression of the mal regulon, especially for genes that encode the glycoporin LamB and maltose transporter, contributed to the osmotolerance phenotype. Conclusions The D654Y single amino acid substitution in RpoB rendered E. coli cells resistant to osmotic stress, probably due to improved cell growth and viability via enhanced sugar uptake under stressed conditions, and activated a potential “pre-defense” mechanism under non-stressed conditions. The findings of this work will be useful for bacterial host improvement to enhance its resistance to osmotic stress and facilitate bio-based organic acids production. Electronic supplementary material The online version of this article (doi:10.1186/s12896-017-0337-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Mengyong Xiao
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.,Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xinna Zhu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.,Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China
| | - Hongtao Xu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.,Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China
| | - Jinlei Tang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.,Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China
| | - Ru Liu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.,Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China
| | - Changhao Bi
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.,Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China
| | - Feiyu Fan
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China. .,Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China.
| | - Xueli Zhang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China. .,Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China.
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Pateraki C, Patsalou M, Vlysidis A, Kopsahelis N, Webb C, Koutinas AA, Koutinas M. Actinobacillus succinogenes : Advances on succinic acid production and prospects for development of integrated biorefineries. Biochem Eng J 2016. [DOI: 10.1016/j.bej.2016.04.005] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Tian X, Wang Y, Chu J, Zhuang Y, Zhang S. Enhanced l-lactic acid production in Lactobacillus paracasei by exogenous proline addition based on comparative metabolite profiling analysis. Appl Microbiol Biotechnol 2015; 100:2301-10. [DOI: 10.1007/s00253-015-7136-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Revised: 10/27/2015] [Accepted: 10/30/2015] [Indexed: 11/30/2022]
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L-Lactic acid production benefits from reduction of environmental osmotic stress through neutralizing agent combination. Bioprocess Biosyst Eng 2014; 37:1917-23. [PMID: 24633312 DOI: 10.1007/s00449-014-1166-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 02/26/2014] [Indexed: 10/25/2022]
Abstract
This paper hinged on the combination effect of two different neutralizing agents Ca(OH)2 and NH4OH on the production of L-lactic acid by Lactobacillus paracasei. Present study quantitatively indicated that environmental osmotic pressure (844-1,772 mOsm/kg) exerted minor influence on L-lactic acid production, but a critical level fell on approximately 3,000 mOsm/kg which restricted L-lactic acid production significantly. Once osmotic pressure exceeded 3,600 mOsm/kg, L-lactic acid production ran aground. A new and efficient neutralizing agent-adding strategy was established in this study to procure 2.21-fold enhancement (5.94 g/l/h) relative to previous productivity of L-lactic acid with NH4OH as neutralizing agent via batch cultivation. It was, therefore, speculated that inhibition effect in the late phase of the fermentation might be in large part attributed to the dramatic increase of environmental osmotic stress, other than cumulative effect of lactate concentration itself.
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