Mukhtar Hamid, Suliman Syed Muhammad, Shabbir Aroosh, Mumtaz Muhammad Waseem, Rashid Umer, Rahimuddin Sawsan Abdulaziz
Institute of Industrial Biotechnology, Government College University, Lahore 54000, Pakistan.
Department of Chemistry, University of Gujrat, Gujrat, Pakistan.
Protein Pept Lett. 2018;25(2):195-201. doi: 10.2174/0929866525666180122112805.
Lipid-producing microorganisms, said to be oleaginous have been recognized since several years. We had investigated the effects of medium components and culturing situations on cell growth and lipid accumulation of oleaginous yeasts which were analytically examined so as to enhance lipid yield for biodiesel production.
The main objective of this study was to explore oleaginous yeast, Yarrowia lipolytica isolated from soil and optimization of culture conditions and medium components to obtained better quality microbial oil for biodiesel production.
Fifty yeast strains were isolated from soil from different regions of Lahore and eleven of them were selected for oil production. The isolated yeast colonies were screened to further check their lipid producing capabilities by the qualitative analysis. Five yeast strains were designated as oleaginous because they produced more than 16% of oil based on their biomass. To estimate the total lipid content of yeast cells, the extraction of lipids was done by performing the procedure proposed by Bligh and Dyer. The transesterification of yeast oils was performed by using different methods. There were three different strategies customized to transesterifying microbial oil using base catalyzed transesterification, acid catalyzed transesterification and enzyme-based transesterification. After completion of transesterification, sample was used for fatty acid methyl esters (FAMEs) were analyzed by gas-chromatograph with ionization detector type MS.
The isolate IIB-10 identified as Yarrowia lipolytica produced maximum amount of lipids i.e. 22.8%. More amount of biomass was obtained when cane molasses was utilized as carbon source where it produced 29.4 g/L of biomass while sucrose and lactose were not utilized by IIB-10 and no biomass was obtained. Similarly, meat extracts showed best results when it was used as nitrogen source because it resulted in 35.8 g/L biomass of Yarrowia lipolytica IIB-10. The culturing conditions like size of inoculum, effect of pH and time of incubation were also studied. The 10% of inoculum size produced 25.4 g/L biomass at 120 h incubation time, while the pH 7 was the optimum pH at which 24.8 g/L biomass was produced by Yarrowia lipolytica IIB-10. GC-MS analysis showed that biodiesel produced by transesterification contained similar fatty acids as found in vegetable oil for this reason it is widely accepted feedstock for biodiesel production.
The analysis of fatty acids methyl esters showed the similar composition of microbial oil as in vegetable oils and high amount of methyl esters were obtained after transesterification. Therefore, potentially oleaginous yeast could be used to generate a large amount of lipids for biodiesel production that will be the better substitute of petroleum-based diesel and will also control the environmental pollution.
能产生脂质的微生物，即所谓的产油微生物，多年来已为人所知。我们研究了培养基成分和培养条件对产油酵母细胞生长和脂质积累的影响，并进行了分析检测，以提高生物柴油生产的脂质产量。
本研究的主要目的是探索从土壤中分离出的产油酵母解脂耶氏酵母，优化培养条件和培养基成分，以获得质量更好的用于生物柴油生产的微生物油脂。
从拉合尔不同地区的土壤中分离出50株酵母菌株，其中11株被选来进行油脂生产。通过定性分析对分离出的酵母菌落进行筛选，以进一步检查它们的产脂能力。5株酵母菌株被认定为产油酵母，因为它们基于生物量产生的油脂超过16%。为了估计酵母细胞的总脂质含量，按照布莱和戴尔提出的方法进行脂质提取。使用不同方法对酵母油脂进行酯交换反应。有三种不同的策略用于微生物油脂的酯交换反应，即碱催化酯交换反应、酸催化酯交换反应和酶促酯交换反应。酯交换反应完成后，将样品用于通过带质谱电离检测器的气相色谱仪分析脂肪酸甲酯（FAMEs）。
鉴定为解脂耶氏酵母的分离株IIB - 10产生的脂质量最多，即22.8%。当使用甘蔗糖蜜作为碳源时获得了更多的生物量，此时它产生了29.4 g/L的生物量，而IIB - 10不利用蔗糖和乳糖，未获得生物量。同样，当使用肉提取物作为氮源时效果最佳，因为它使解脂耶氏酵母IIB - 10的生物量达到35.8 g/L。还研究了接种量大小、pH值影响和培养时间等培养条件。10%的接种量在培养120小时时产生了25.4 g/L的生物量，而pH 7是最佳pH值，此时解脂耶氏酵母IIB - 10产生了24.8 g/L的生物量。气相色谱 - 质谱分析表明，酯交换反应产生的生物柴油所含脂肪酸与植物油中的相似，因此它是生物柴油生产中广泛接受的原料。
脂肪酸甲酯分析表明微生物油脂的组成与植物油相似，酯交换反应后获得了大量的甲酯。因此，潜在的产油酵母可用于为生物柴油生产产生大量脂质，这将是石油基柴油的更好替代品，也将控制环境污染。
