Sharma Shalley, Arora Anju, Sharma Pankhuri, Singh Surender, Nain Lata, Paul Debarati
Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.
Amity Institute of Biotechnology, Amity University, Noida, U.P., India.
Chem Cent J. 2018 Feb 5;12(1):8. doi: 10.1186/s13065-018-0375-8.
Bioethanol obtained by fermenting cellulosic fraction of biomass holds promise for blending in petroleum. Cellulose hydrolysis yields glucose while hemicellulose hydrolysis predominantly yields xylose. Economic feasibility of bioethanol depends on complete utilization of biomass carbohydrates and an efficient co-fermenting organism is a prerequisite. While hexose fermentation capability of Saccharomyces cerevisiae is a boon, however, its inability to ferment pentose is a setback.
Two xylose fermenting Kodamaea ohmeri strains were isolated from Lagenaria siceraria flowers through enrichment on xylose. They showed 61% glucose fermentation efficiency in fortified medium. Medium engineering with 0.1% yeast extract and peptone, stimulated co-fermentation potential of both strains yielding maximum ethanol 0.25 g g on mixed sugars with ~ 50% fermentation efficiency. Strains were tolerant to inhibitors like 5-hydroxymethyl furfural, furfural and acetic acid. Both K. ohmeri strains grew well on biologically pretreated rice straw hydrolysates and produced ethanol.
This is the first report of native Kodamaea sp. exhibiting notable mixed substrate utilization and ethanol fermentation. K. ohmeri strains showed relevant traits like utilizing and co-fermenting mixed sugars, exhibiting excellent growth, inhibitor tolerance, and ethanol production on rice straw hydrolysates.
通过发酵生物质的纤维素部分获得的生物乙醇有望与石油混合使用。纤维素水解产生葡萄糖，而半纤维素水解主要产生木糖。生物乙醇的经济可行性取决于生物质碳水化合物的完全利用，而高效的共发酵生物是前提条件。虽然酿酒酵母的己糖发酵能力是一个优势，但其无法发酵戊糖却是一个障碍。
通过在木糖上富集培养，从瓠瓜花中分离出两株木糖发酵的欧默柯达酵母菌株。它们在强化培养基中显示出61%的葡萄糖发酵效率。用0.1%酵母提取物和蛋白胨进行培养基工程改造，刺激了两株菌株的共发酵潜力，在混合糖上产生的最大乙醇量为0.25 g/g，发酵效率约为50%。这些菌株对5-羟甲基糠醛、糠醛和乙酸等抑制剂具有耐受性。两株欧默柯达酵母菌株在生物预处理的稻草水解产物上生长良好并产生乙醇。
这是关于本地柯达酵母属表现出显著的混合底物利用和乙醇发酵的首次报道。欧默柯达酵母菌株表现出相关特性，如利用和共发酵混合糖、在稻草水解产物上表现出良好的生长、抑制剂耐受性和乙醇生产能力。
