Amaranth seeds (Amaranthus palmeri L.) as novel feedstock for biodiesel production by oleaginous yeast

Enhanced biodiesel and β-carotene production in Rhodotorula pacifica INDKK using sugarcane bagasse and molasses by an integrated biorefinery framework

Dependency on fossil fuels raises an economic and ecological concern that has urged to look for alternative sources of energy. Bio-refinery concept is one of the alternate frameworks for the biomass conversion into biofuel and other value-added by-products. The present work illustrates importance of an oleaginous yeast Rhodotorula pacifica INDKK in an integrated bio-refinery field by utilizing renewable sugars generated from lignocellulosic biomass. The maximum 11.8 g/L lipid titer, 210.4 mg/L β-carotene and 7.1 g animal feed were produced by R. pacifica INDKK in bioreactor containing 5% (v/v) molasses supplemented with enzymatically hydrolyzed and alkali-pretreated sugarcane bagasse hydrolysate (35% v/v). Furthermore, xylooligosaccharides (20.6 g/L), a beneficial prebiotics were also produced from the hemicellulosic fraction separated after alkali pretreatment of bagasse. This novel concept of integrated yeast bio-refinery for concomitant production of biodiesel and multiple value-added products with minimum waste generation is proposed as a sustainable and profitable process.

The history, state of the art and future prospects for oleaginous yeast research

Lipid-based biofuels, such as biodiesel and hydroprocessed esters, are a central part of the global initiative to reduce the environmental impact of the transport sector. The vast majority of production is currently from first-generation feedstocks, such as rapeseed oil, and waste cooking oils. However, the increased exploitation of soybean oil and palm oil has led to vast deforestation, smog emissions and heavily impacted on biodiversity in tropical regions. One promising alternative, potentially capable of meeting future demand sustainably, are oleaginous yeasts. Despite being known about for 143 years, there has been an increasing effort in the last decade to develop a viable industrial system, with currently around 100 research papers published annually. In the academic literature, approximately 160 native yeasts have been reported to produce over 20% of their dry weight in a glyceride-rich oil. The most intensively studied oleaginous yeast have been Cutaneotrichosporon oleaginosus (20% of publications), Rhodotorula toruloides (19%) and Yarrowia lipolytica (19%). Oleaginous yeasts have been primarily grown on single saccharides (60%), hydrolysates (26%) or glycerol (19%), and mainly on the mL scale (66%). Process development and genetic modification (7%) have been applied to alter yeast performance and the lipids, towards the production of biofuels (77%), food/supplements (24%), oleochemicals (19%) or animal feed (3%). Despite over a century of research and the recent application of advanced genetic engineering techniques, the industrial production of an economically viable commodity oil substitute remains elusive. This is mainly due to the estimated high production cost, however, over the course of the twenty-first century where climate change will drastically change global food supply networks and direct governmental action will likely be levied at more destructive crops, yeast lipids offer a flexible platform for localised, sustainable lipid production. Based on data from the large majority of oleaginous yeast academic publications, this review is a guide through the history of oleaginous yeast research, an assessment of the best growth and lipid production achieved to date, the various strategies employed towards industrial production and importantly, a critical discussion about what needs to be built on this huge body of work to make producing a yeast-derived, more sustainable, glyceride oil a commercial reality.

Recent Advances in Feedstock and Lipase Research and Development towards Commercialization of Enzymatic Biodiesel

Biodiesel is a biodegradable, renewable, and carbon-neutral alternative to petroleum diesel that can contribute to the global effort of minimizing the use of fossil fuels and meeting the ever-growing energy demands and stringent environmental constraints. The aim of this work was to (1) review the recent progress in feedstock development, including first, second, third, and fourth-generation feedstocks for biodiesel production; (2) discuss recent progress in lipase research and development as one of the key factors for establishing a cost-competitive biodiesel process in terms of enzyme sources, properties, immobilization, and transesterification efficiency; and (3) provide an update of the current challenges and opportunities for biodiesel commercialization from techno-economic and social perspectives. Related biodiesel producers, markets, challenges, and opportunities for biodiesel commercialization, including environmental considerations, are critically discussed.

Harnessing pongamia shell hydrolysate for triacylglycerol agglomeration by novel oleaginous yeast Rhodotorula pacifica INDKK

BACKGROUND

To meet the present transportation demands and solve food versus fuel issue, microbial lipid-derived biofuels are gaining attention worldwide. This study is focussed on high-throughput screening of oleaginous yeast by microwave-aided Nile red spectrofluorimetry and exploring pongamia shell hydrolysate (PSH) as a feedstock for lipid production using novel oleaginous yeast Rhodotorula pacifica INDKK.

RESULTS

A new oleaginous yeast R. pacifica INDKK was identified and selected for microbial lipid production. R. pacifica INDKK produced maximum 12.8 ± 0.66 g/L of dry cell weight and 6.78 ± 0.4 g/L of lipid titre after 120 h of growth, showed high tolerance to pre-treatment-derived inhibitors such as 5-hydroxymethyl furfural (5-HMF), (2 g/L), furfural (0.5 g/L) and acetic acid (0.5 g/L), and ability to assimilate C3, C5 and C6 sugars. Interestingly, R. pacifica INDKK showed higher lipid accumulation when grown in alkali-treated saccharified PSH (AS-PSH) (0.058 ± 0.006 g/L/h) as compared to acid-treated detoxified PSH (AD-PSH) (0.037 ± 0.006 g/L/h) and YNB medium (0.055 ± 0.003 g/L/h). The major fatty acid constituents are oleic, palmitic, linoleic and linolenic acids with an estimated cetane number (CN) of about 56.7, indicating the good quality of fuel.

CONCLUSION

These results suggested that PSH and R. pacifica INDKK could be considered as potential feedstock for sustainable biodiesel production.

An Overview of Potential Oleaginous Microorganisms and Their Role in Biodiesel and Omega-3 Fatty Acid-Based Industries

Microorganisms are known to be natural oil producers in their cellular compartments. Microorganisms that accumulate more than 20% w/w of lipids on a cell dry weight basis are considered as oleaginous microorganisms. These are capable of synthesizing vast majority of fatty acids from short hydrocarbonated chain (C6) to long hydrocarbonated chain (C36), which may be saturated (SFA), monounsaturated (MUFA), or polyunsaturated fatty acids (PUFA), depending on the presence and number of double bonds in hydrocarbonated chains. Depending on the fatty acid profile, the oils obtained from oleaginous microorganisms are utilized as feedstock for either biodiesel production or as nutraceuticals. Mainly microalgae, bacteria, and yeasts are involved in the production of biodiesel, whereas thraustochytrids, fungi, and some of the microalgae are well known to be producers of very long-chain PUFA (omega-3 fatty acids). In this review article, the type of oleaginous microorganisms and their expertise in the field of biodiesel or omega-3 fatty acids, advances in metabolic engineering tools for enhanced lipid accumulation, upstream and downstream processing of lipids, including purification of biodiesel and concentration of omega-3 fatty acids are reviewed.

Novel integration of biohydrogen production with fungal biodiesel production process

An integration of bio-H₂ with fungal biodiesel production process was investigated. Highest cumulative H₂ production of 3.3 ± 0.20 L L^-1 was observed during media optimization using mixture design. Using optimized media composition, continuous H₂ production at 0.2 h^-1 dilution rate, showed highest H₂ production rate, H₂ yield and biomass yield of 1020 ± 23 mL L^-1 h^-1, 2.8 ± 0.1 mols mol^-1 reducing sugar and 1.2 ± 0.06 g L^-1, respectively. Using the spent media generated from the dark fermentation, oleaginous yeast cultivation was done. Highest biomass and total lipid yield of 6.4 ± 0.20 g L^-1 and 0.46 ± 0.04 g g^-1 was observed at initial 15% v/v inoculums strength, pH of 5, 1.5 L min^-1 aeration rate and 25 °C temperature of cultivation, respectively. Energy recovery improved by 90.3% in integrated process when compared with single stage hydrogen production.

Assessing oil accumulation in the oleaginous yeast Cystobasidium oligophagum JRC1 using dairy waste cheese whey as a substrate

This study assesses the potential for the lipid production by the oleaginous yeast Cystobasidium oligophagum JRC1 using dairy industry waste cheese whey as a substrate. Cheese whey was used either untreated (UCW) or deproteinized (DCW) at different concentrations (25-100%) to serve as the carbon and energy source. Both UCW and DCW supported high biomass and lipid productivities. The biomass productivity of 0.076 ± 0.0004 and 0.124 ± 0.0021 g/L h, lipid productivity of 0.0335 ± 0.0004 and 0.0272 ± 0.0008 g/L h, and the lipid content of 44.12 ± 0.84 and 21.79 ± 1.00% were achieved for 100% DCW and UCW, respectively. The soluble chemical oxygen demand (sCOD) removal rate was 8.049 ± 0.198 and 10.61 ± 0.0165 g/L day (84.91 ± 0.155 and 86.82 ± 0.067% removal) for 100% DCW and UCW, respectively. Fatty acid methyl ester (FAME) composition obtained using GC-FID studies revealed the presence of C16 and C18 fatty acid in the lipid extract and the biodiesel properties were found to be in accordance with ASTM and EN standards. The study presents a method for the valorization of cheese whey waste into a feasible feedstock for biodiesel.

An Overview of Current Pretreatment Methods Used to Improve Lipid Extraction from Oleaginous Micro-Organisms

Microbial oils, obtained from oleaginous microorganisms are an emerging source of commercially valuable chemicals ranging from pharmaceuticals to the petroleum industry. In petroleum biorefineries, the microbial biomass has become a sustainable source of renewable biofuels. Biodiesel is mainly produced from oils obtained from oleaginous microorganisms involving various upstream and downstream processes, such as cultivation, harvesting, lipid extraction, and transesterification. Among them, lipid extraction is a crucial step for the process and it represents an important bottleneck for the commercial scale production of biodiesel. Lipids are synthesized in the cellular compartment of oleaginous microorganisms in the form of lipid droplets, so it is necessary to disrupt the cells prior to lipid extraction in order to improve the extraction yields. Various mechanical, chemical and physicochemical pretreatment methods are employed to disintegrate the cellular membrane of oleaginous microorganisms. The objective of the present review article is to evaluate the various pretreatment methods for efficient lipid extraction from the oleaginous cellular biomass available to date, as well as to discuss their advantages and disadvantages, including their effect on the lipid yield. The discussed mechanical pretreatment methods are oil expeller, bead milling, ultrasonication, microwave, high-speed and high-pressure homogenizer, laser, autoclaving, pulsed electric field, and non-mechanical methods, such as enzymatic treatment, including various emerging cell disruption techniques.