Biodiesel production from Stichococcus strains at laboratory scale

BACKGROUND: This paper reports the results of an experimental campaign of autotrophic cultures of Stichococcus strains aiming at selecting the most promising strain for biofuel production. The strain selected—S. bacillaris 158/11—was cultivated in 1 L lab‐scale bubble column photobioreactors under fed‐batch and semi‐continuous conditions. A Bold basal medium supplemented with NaNO₃ as nitrogen source was adopted. Tests were carried out at 23 °C, 140 µE m^?2 s^?1, and air flow rate ranging between 0.4 and 4 vvm. Cultures were characterized in terms of pH, concentration of total nitrogen, total organic carbon, total inorganic carbon, biomass, lipid fraction and methyl‐ester distribution of transesterified lipids. RESULTS: S. bacillaris 158/11 proved to be the best strain to produce biodiesel. Methyl‐ester distribution was characterized by a large fraction of methyl palmitate, methyl linolenate, methyl linoleate, and methyl oleate along with phytol. The process photosynthetic efficiency—fraction of available light stored as chemical energy ‐ was about 1.5%. Specific biomass productivity was ～60 mg_DM L^?1 day^?1 under the semi‐continuous conditions tested. Total lipid productivity was 14 mg L^?1 day^?1 at a dilution rate of 0.050 L day^?1. CONCLUSION: S. bacillaris 158/11 is a potential strain for massive microalgae cultures for biofuel production. Higher biomass/total‐lipid productivity could be obtained in sunlight. Copyright © 2011 Society of Chemical Industry     

能源植物菊芋制备生物基化合物研究进展

生物质作为工业填料在制备化学品的过程中具有可再生性、碳元素利用平衡等优点，但大部分能源植物存在来源于粮食必需品、与农作物争夺优质土地的问题。天然生物质菊芋因具有优良的生长特性、糖类组分含量高、单体官能团多样等特点，被认为是未来最重要的非粮能源植物之一。本文介绍了通过物理过程、生物过程及化学过程等不同途径高附加值化菊芋的研究进展，总结不同方式制备生物基化合物的特点。基于菊芋主要因其根茎中含有丰富的不易被人体消化的菊糖、果糖基多糖聚合度低、组成多糖和还原糖的碳源单体高度单一等优点，着重介绍目前菊芋根茎作为底物制备生物基化合物的过程，分析了通过化学催化法或发酵法制备多元醇、5-羟甲基糠醛、乳酸酯等产品的反应条件、催化剂或生物酶的类型等。基于菊芋秸秆中富含纤维素、半纤维素和木质素等木质纤维素的优势，简述了以纤维素和半纤维素类碳水化合物和木质素的主要研究现状，以及对菊芋秸秆直接催化转化的效果，突出菊芋秸秆转化的优势，提出菊芋秸秆作为底物高效制备目标产物的改进措施。对菊芋根茎和菊芋秸秆的高附加值化过程和效果的分析表明，加强对非粮能源植物菊芋的深加工与生物、化学转化技术的研究，配合生物法与化学法相结合的手段，能加快菊芋工业化应用取得实质性的进展。     

Simultaneous harvesting and cell disruption of microalgae using ozone bubbles: optimization and characterization study for biodiesel production

In the present study, ozone was introduced as an alternative approach to harvest and disrupt microalgae cells (Chlorella vulgaris) simultaneously for biodiesel production. At the optimum ozonation conditions (6.14 g·h^–1 ozone concentration, 30 min ozonation time, 1 L·min^–1 of ozone flowrate at medium pH of 10 and temperature of 30 °C), the sedimentation efficiency of microalgae cells increased significantly from 12.56% to 68.62%. It was observed that the microalgae cells aggregated to form flocs after pre-treated with ozone due to the increment of surface charge from –20 to –6.59 mV. Besides, ozone had successfully disrupted the microalgae cells and resulted in efficient lipid extraction, which was 1.9 times higher than the control sample. The extracted microalgae lipid was mainly consisted of methyl palmitate (C16:0), methyl oleate (C18:1) and methyl linolenate (C18:3), making it suitable for biodiesel production. Finally, utilization of recycled culture media after ozonation pre-treatment showed robust growth of microalgae, in which the biomass yield was maintained in the range of 0.796 to 0.879 g·h^–1 for 5 cycles of cultivation.     

Effects of the ratio of carbon to nitrogen concentration on lipid production by bacterial consortium of sewage sludge using food wastewater as a carbon source

Food wastewater (FWW) and sewage sludge (SS) were used to control the C:N ratio in cultures as a method to increase lipid production by microbial species in SS. FWW and SS were mixed in volumetric ratios (FWW: SS) of 5: 0 (F5), 4: 1 (F4), or 3: 2 (F3). Compared to raw SS, total lipid content production was increased by 263% in F5, 142% in F4, and 111% in F3. These results were caused by increases in the concentrations of triglycerides (TAGs) during lipid enhancement. The fatty acid methyl ester content of TAGs (wt% of extract) was 25.3 in F5, 20.2 in F4 and 13.25 in F3; these were significant improvements over biodiesel production using raw SS. C16:0 fatty acid was mostly converted to C18:1 fatty acid; this is an important result because the proportion of C18:1 strongly influences the quality of biodiesel. This is the first effort to produce biodiesel using FWW instead of synthetic medium as a carbon source. Hence, this study provides a useful solution for treating organic wastes (SS and FWW) simultaneously; this strategy may be an economically viable method for producing biodiesel from organic wastes.     

Lipase-catalyzed methanolysis of microalgae oil for biodiesel production and PUFAs concentration

A novel process with the combined use of lipase NS81006 and Novozym435 was developed for the conversion of microalgae oils for biodiesel production and PUFAs concentration. It was found that during the first-step reaction catalyzed by NS81006, the reaction rates of PUFAs were much slower compared to those with carbon length varying from C14 to C18, but significant increase for PUFAs' conversion was achieved with Novozym435 as the catalyst for the second step conversion. A fatty acid methyl ester (FAME) yield of 95% could be obtained with this two-step enzymatic catalysis. This process has great prospect for converting microalgae oils for biodiesel preparation and PUFAs concentration.     

Integration of biofuels intermediates production and nutrients recycling in the processing of a marine algae

The cost‐effective production of liquid biofuels from microalgae is limited by several factors such as recovery of the lipid fractions as well as nutrients management. Flash hydrolysis, a rapid hydrothermal process, has been successfully applied to fractionate the microalgal biomass into solid biofuels intermediates while recovering a large amount of the nutrients in the aqueous phase (hydrolyzate) in a continuous flow reactor. The aim of the work is to enhance the quality of a high‐ash containing marine algae Nannochloropsis gaditana as biofuel feedstock while recycling nutrients directly for algae cultivation. Characterization of products demonstrated an increase in extractable lipids from 33.5 to 65.5 wt % (dry basis) while retaining the same fatty acid methyl ester profile, in addition to diminution of more than 70 wt % of ash compared to raw microalgae. Moreover, the hydrolyzate was directly used to grow a microalga of the same genus. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1494–1502, 2017     

Enhanced lipid and biodiesel production from glucose‐fed activated sludge: Kinetics and microbial community analysis

An innovative approach to increase biofuel feedstock lipid yields from municipal sewage sludge via manipulation of carbon‐to‐nitrogen (C:N) ratio and glucose loading in activated sludge bioreactors was investigated. Sludge lipid and fatty acid methyl ester (biodiesel) yields (% cell dry weight, CDW) were enhanced via cultivation in activated sludge bioreactors operated at high initial C:N ratio (≥40:1) and glucose loading (≥40 g L^?1). Under C:N 70, 60 g L^?1 glucose loading, a maximum of 17.5 ± 3.9 and 10.2 ± 2.0% CDW lipid and biodiesel yields, respectively, were achieved after 7 d of cultivation. The cultured sludge lipids contained mostly C₁₆? C₁₈ fatty acids, with oleic acid consistently accounting for 40–50% of the total fatty acids. Microbial composition in activated sludge exposed to C:N 70 shifted toward specific gammaproteobacteria, suggesting their relevance in lipid production in wastewater microbiota and potential value in biofuel synthesis applications. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Klebsiella pneumoniae发酵菊芋生产2,3-丁二醇的初步研究

对Klebsiella pneumoniae发酵菊芋块茎生产2,3-丁二醇进行了初步研究,通过摇瓶实验考察了不同碳源及培养基中微量元素对发酵的影响. 结果表明,菊芋是良好的发酵2,3-丁二醇的底物,以其为底物时产物浓度和生产强度比葡萄糖发酵提高了42%以上,培养基中不添加微量元素对菊芋发酵基本没有影响,因而可简化培养基成分以降低生产成本. 在发酵罐批式流加实验中,发酵56 h菊芋发酵的产物浓度和生产强度分别为81.47 g/L和1.45 g/(L×h),与葡萄糖发酵结果相当.     

Differential fatty acid profiles of Chlorella kessleri grown with organic materials

BACKGROUND: Integration of oleaginous microalgae cultivation with wastewater treatment is considered a low‐cost approach for manufacturing algae‐based biodiesel. However, autotrophic microalgae cannot survive in organic wastewater where the effluent is usually turbid and sunlight cannot penetrate into the wastewater. Thus mixotrophic microalgae should be explored. The objective of this study was to investigate the potential of using mixotrophic Chlorella kessleri to produce fatty acids from organic materials. RESULTS: Results revealed that mixotrophic C. kessleri fatty acids display much greater productions (up to 54.67% of cell dry weight) and more suitable compositions for biodiesel production (moderate carbon chain length mainly with C16 and C18, down to 1.17 ?/mol of unsaturation degree) than autotrophic ones. A suitable final pH (near neutral) after nitrate‐depletion and a high organic carbon consumption seemed to be the key factors manipulating fatty acids production under whichever organic substrate tested. CONCLUSION: These characteristics increase the acceptability in using mixotrophic C. kessleri as a potential easy‐control candidate in biodiesel production. If fed with available organic effluent of wastewater as the nutrient supply, C. kessleri may have great potential for profitable biodiesel. © 2012 Society of Chemical Industry     

两步法催化高酸价微藻油脂制备生物柴油

研究了两步法催化高酸价微藻油脂制备生物柴油的工艺条件。测定从产油栅藻培养物中提取的油脂的化学成分,发现油脂的游离脂肪酸含量分布在10%~32%,极性脂含量分布在21%~46%。以此高酸价、高极性脂含量油脂,经过酸预酯化-碱催化转酯化两步法制备生物柴油。其最优反应条件为:30%的醇加入量,1%油质量的硫酸催化反应2 h,其油脂酸价可从初始酸值的17~46 mg/g降低至2 mg/g以下;随后,在醇油物质的量之比为12:1,催化剂氢氧化钾用量为油质量的2%,65℃条件下反应30min,制备所得生物柴油中脂肪酸甲酯的质量分数可达96.6%,甘油三酯的转化效率接近100%。根据《柴油机燃料调合用生物柴油》国家标准,测定了微藻生物柴油产品的品质指标,发现其密度、运动黏度、酸价、氧化安定性等各项指标均符合国家标准(GB/T 20828-2007);热值为39.76 MJ/kg,符合欧盟生物柴油标准(EN 14214)。     

Cultivation of microalgae for biodiesel production: A review on upstream and downstream processing

Fluctuating market price of fossil fuel and overwhelming emission of greenhouse gases to the atmosphere have resulted in climate change and have been a global concern in this decade.Hence,biodiesel has become an alternative option to fossil diesel as it is renewable and environmentally friendly.Nevertheless,this alternative fuel that is usually derived from terrestrial oil crops will cause shortage in food supply and deforestation if mass production is realized.In recent years,cultivation of aquatic microorganism (particularly microalgae) to produce biodiesel is considered as a practical solution due to their high growth rate and ability to synthesize large quantity of lipid within their cell.However,the development of energy and cost-efficiency of microalgae cultivation system are the main issues in producing renewable microalgae biodiesel.Of late,wastewater or organic compost has been used as the cultivation medium as it can provide sufficient nutrients to sustain microalgae growth.Microalgae cultivation method and system are vitally important as these factors undoubtedly affect the final microalgae biomass and lipid yield.In this review,the cultivation system of microalgae,nutrients demanded for microalgae production,cell harvesting and drying,microalgae oil extraction,and utilization of microalgae biomass for biodiesel production are introduced and discussed.It is anticipated to convey clearer perspectives in upstream and downstream processes in microalgae-derived biodiesel production.     

Enhanced microbial oil production by activated sludge microorganisms via co‐fermentation of glucose and xylose

The co‐fermentation of glucose and xylose by activated sludge microorganisms for the production of microbial oils for use as biodiesel feedstock was investigated. Various carbon sources at initial concentration of 60 g/L and C:N ratio 70:1 were investigated: xylose, glucose, and 2:1 and 1:2 (by mass) glucose/xylose mixtures. Oil accumulation ranged between 12 to 22% CDW, the highest of which was obtained when xylose was the sole substrate used. Kinetic modeling of the fermentation data showed that specific growth and oil accumulation rates were similar in all substrate types and the lipid coefficient ranged from 0.02 to 0.06 g/g of sugar consumed. The fatty acid methyl ester yield and composition of the lipids showed their suitability for conversion to biodiesel. Based on the results, lignocellulose sugars could be used as fermentation substrates by activated sludge microorganisms for enhancing the oil content of sewage sludge for its use as a sustainable biofuel feedstock source. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4036–4044, 2013     

Advances in cultivation and processing techniques for microalgal biodiesel: A review

The key technologies for producing microalgal biodiesel include microalgae screening, economical cultivation, and efficient methods in lipid extraction and conversion. Recent advances in microalgae cultivation, lipid extraction, and biodiesel preparation are reviewed in this work, with emphasis on photosynthetic metabolisms, separation efficiency and catalytic kinetics. The mutual exclusion between lipid accumulation and fast growth limits total lipid productivity, while only triglycerides in neutral lipids are converted to biodiesel through transesterification. The hurdles in large scale culture and low neural lipids yield are discussed, as well as the relationship between high unsaturation and fuel properties. This review aims to provide technical information to guide strain screening and lipid conversion for microalgal biodiesel industry.     

Production of lipid from N‐acetylglucosamine by Cryptococcus curvatus

N‐Acetylglucosamine (GlcNAc), the monomeric constituent of chitin, is rarely used as a carbon source for fermentation technology. In this study, we demonstrate that the oleaginous yeast Cryptococcus curvatus ATCC 20509 can produce intracellular lipid during the cultivation process and total lipid content can reach 54% on a GlcNAc‐based medium. Culture of C. curvatus under various conditions indicated that lipid accumulation also occurred at a relatively broad range of temperatures as well as relatively high initial GlcNAc concentrations. Fatty acid analysis indicated that the product was rich in palmitic acid, stearic acid, and oleic acid, closely resembling the composition of palm oil. More importantly, the lipid sample produced at 22 °C had a total saturated fatty acid content of 54.2 wt%, suggesting that it may be explored as cocoa‐butter equivalent. Our data suggested that GlcNAc could be used as a feedstock for industrial biotechnology and that C. curvatus ATCC 20509 is a strain capable of accumulating high intracellular lipid using this nitrogen‐rich renewable material. Practical applications: Microbial lipid is a versatile material, especially for biodiesel production. Stable and abundant renewable raw substrates remain to be explored for large‐scale production of microbial lipid. The present work reports lipid production using N‐acetylglucosamine (GlcNAc) by the oleaginous yeast Cryptococcus curvatus ATCC 20509 to yield up to 54% intracellular lipid content. More significantly, the lipid sample produced at 22 °C had a total saturated fatty acid content of 54.2 wt%, suggesting that it may be explored as cocoa‐butter equivalent. Our technology provides the opportunity to effectively convert GlcNAc, available from one of the most abundant renewable materials chitin, into lipid. This procedure should prove valuable in terms of renewable energy production as well as environmental pollution control.     

酵母油脂及用于生物柴油制备研究进展

油脂酵母具有高产油能力,并且所积累油脂的主要成分与植物油脂相似,可作为生物柴油制备的原料。本文对影响酵母油脂合成的关键酶、基因、碳源以及酵母油脂在生物柴油制备中的研究进展进行了综述,认为ATP∶柠檬酸裂解酶和苹果酸酶是酵母油脂合成代谢途径中的关键酶,另外,LRO1、DGA1和ARE基因也被认为同油脂合成有着紧密联系。对酵母油脂用于生物柴油生产的前景进行了展望：利用廉价碳源如甘油、能源作物以及木质纤维素水解液等培养酵母,可有效降低生产成本。在不同催化方法下,酵母油脂均可用于制备生物柴油,这对进一步研究生物柴油的生产应用有着重要意义。     

Variables affecting the in situ transesterification of microalgae lipids

This paper describes the effect of important reaction variables on the production of biodiesel from non-edible microalgae lipids, using the acid-catalysed in situ transesterification process. The specific gravity of the biodiesel product was used to monitor the conversion progress. The results indicate that increasing the reacting alcohol volume and the temperature lead to improved fatty acid methyl ester (FAME) conversions. With the exception of in situ transesterification carried out at room temperature (23 °C), the equilibrium FAME conversions appear to approach asymptotic limits for reaction times greater than 8 h for all temperatures investigated. Stirring the reaction vessel had a significant positive influence on the rate of biodiesel formation. Increasing the moisture content of the microalgae biomass had a strong negative influence on the equilibrium FAME yield, and in situ transesterification was inhibited when the biomass water content was greater than 115% w/w (based on oil weight).     

Effects of Acetic Acid on Growth and Lipid Production by Cryptococcus albidus

The cell growth and lipid accumulation process of Cryptococcus albidus were investigated using acetic acid as the sole carbon source at different concentrations. C. albidus showed high tolerance to acetic acid at a high concentration of 30 g L^?1. The highest lipid content (32.69 ± 0.50 %) and lipid yield (0.96 ± 0.05 g L^?1) were both obtained in the medium with an initial acetic acid concentration of 30 g L^?1 on day five. Interestingly, the maximum lipid content and lipid yield was obtained on a different day in a medium with different acetic acid concentration. The fatty acid composition of the lipids accumulated by C. albidus was 16–23 % palmitic acid (C16:0), 3–5 % linolenic acid (C18:3), 42–51 % linoleic acid (C18:2) and 23–27 % oleic acid (C18:1), which was similar to that of soybean oil; thus, this microbial oil has great potential value as a renewable biodiesel feedstock. This work also provides valuable information for further research to use cheap substrates containing a high concentration of acetic acid (such as lignocellulosic hydrolysates), which is an economical and environmentally friendly form of microbial oil production.     

Microalgae biodiesel via in situ methanolysis

BACKGROUND: Microalgae have recently been considered a potential feedstock for biodiesel production, since they do not compete with agricultural land, unlike oil crops. However, the production processes must be energetically and economically viable. Therefore, an in situ methanolysis process is proposed for biodiesel production directly from microalgae biomass, to avoid the need for the separation and extraction steps. RESULTS: Biodiesel was obtained using methanol as the methylation reactant for the transesterification reaction and hydrochloric acid as the catalyst precursor, at 80 °C for 2 h of reaction. A mass return of 23.07 ± 2.76% (m/m) was obtained. Spectrometry in the infrared region showed that the product had equivalent bands of axial deformation of C?O, C? O and C? H, i.e. an ester. Tests showed the chromatographic profile of fatty acids in the sample. A process energetic efficiency value of 1.17 was obtained for microalgae derived biodiesel, which is higher than from soybean and sunflower, reportedly 1.06 and 1.12. CONCLUSIONS: Industrial sustainability results from low energetic, economic and environmental losses. The microalgae in situ methanolysis process showed greater fuel available energy than energy consumption, therefore is energetically sustainable. Economic and environmental issues should still be addressed. Copyright © 2011 Society of Chemical Industry     

Growth kinetics and lipid production using Chlorella vulgaris in a circulating loop photobioreactor

BACKGROUND: Compared with agriculture, microalgae culture promises to be a novel way of producing lipids for both food consumption and transportation fuel (biodiesel) purposes while using a minimal amount of land area. A circulating loop photobioreactor has been used to study the growth kinetics and lipid yield of Chlorella vulgaris growing on carbon dioxide as the sole source of carbon. RESULTS: Because of high photosynthetic active radiation (PAR) fluxes, C. vulgaris was observed to grow in exponential mode. The highest growth rate achieved was 0.049 h^?1 at the optimum growth conditions of 71.8 mW L^?1 PAR density, 10% CO₂ (v/v) in air and with an applied 8 h dark phase. The microalgae was observed to grow in a Monod fashion with a PAR density saturation coefficient of 2.8 mW L^?1. Light intensity showed the potential to significantly increase lipid yield, which reached a maximum of 30% (by mass) of cell dry weight. CONCLUSION: The circulating loop photobioreactor is a low‐cost bioreactor technology capable of culturing photosynthetic microalgae at high PAR densities and with uniform mixing and lighting. C. vulgaris is able to grow exponentially in this bioreactor and produce lipids at concentrations up to 30% by cell dry weight. Copyright © 2011 Society of Chemical Industry     

Ozone for Microalgae Biomass Harvesting from Wastewater

The use of ozone has been investigated as a harvesting technique (ozone-flotation) for microalgae recovery from wastewater. This document summarizes the most outstanding results achieved to date by our working group, including the ozone effect on the lipid and fatty acid methyl ester (FAME) content. Additionally, the effect of the initial concentration of microalgal biomass on ozone-flotation was investigated using microalgae Scenedesmus sp. cultured in wastewater. Ozone-flotation required specific conditions to separate biomass from wastewater, depending on the type of microalgae strain, culture (single or mixed) and concentration. The effect of ozone-treatment improved lipid extractability and increased degree of FAME saturation.