Phenotypic selection of a wild Saccharomyces cerevisiae strain for simultaneous saccharification and co-fermentation of AFEX™ pretreated corn stover.
Phenotypic selection of a wild Saccharomyces cerevisiae strain for simultaneous saccharification and co-fermentation of AFEX™ pretreated corn stover.
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DOI：
10.1186/1754-6834-6-108
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发表时间：
2013
影响因子：
6.3
通讯作者：
Sato TK
中科院分区：
文献类型：
--
作者：
Jin M;Sarks C;Gunawan C;Bice BD;Simonett SP;Avanasi Narasimhan R;Willis LB;Dale BE;Balan V;Sato TK
同步糖化-共发酵(SSCF)工艺包括木质纤维素预处理后的酶解和葡萄糖和木糖在一个生物反应器中的发酵。酶解的最适温度高于产乙醇型酿酒酵母的标准发酵温度。此外，生物质预处理产生的降解产物不利于糖的发酵，尤其是木糖的发酵，并能与高温胁迫协同作用。解决这两个问题的一种方法是利用对高温和降解产物具有天生耐受性的菌株背景。在这项研究中，我们筛选了108株野生和驯化的酿酒酵母菌株，这些菌株来自广泛的环境生态位。根据其对同时高温和™(氨纤维膨胀)降解产物的生长耐受性，选择了一株野生菌株。将木糖还原酶基因、木糖醇脱氢酶基因和木糖酸激酶基因分别转化到树干裂解酵母菌株中，比较了该工程菌与424A(LNH-ST)菌株在标准实验室培养基和AFEX玉米秸秆水解物以及不同温度下的玉米秸秆超临界流体中生产乙醇和发酵木糖的能力。在35°C的9%(w/w)葡聚糖负载ACS的SSCF中，与基准菌株424A(LNH-ST)相比，工程菌株显示出更高的细胞存活率和相似的乙醇量(51.3g/L)。这些结果验证了我们的方法在筛选具有耐热和耐降解产物特性的野生酿酒酵母生产木质纤维生物燃料方面的有效性。在这项工作中表现型的野生和驯化的酵母菌株公开可供其他人用作在高温下发酵其经过预处理的生物质的遗传背景。
Simultaneous saccharification and co-fermentation (SSCF) process involves enzymatic hydrolysis of pretreated lignocellulosic biomass and fermentation of glucose and xylose in one bioreactor. The optimal temperatures for enzymatic hydrolysis are higher than the standard fermentation temperature of ethanologenic Saccharomyces cerevisiae. Moreover, degradation products resulting from biomass pretreatment impair fermentation of sugars, especially xylose, and can synergize with high temperature stress. One approach to resolve both concerns is to utilize a strain background with innate tolerance to both elevated temperatures and degradation products. In this study, we screened a panel of 108 wild and domesticated Saccharomyces cerevisiae strains isolated from a wide range of environmental niches. One wild strain was selected based on its growth tolerance to simultaneous elevated temperature and AFEX™ (Ammonia Fiber Expansion) degradation products. After engineering the strain with two copies of the Scheffersomyces stipitis xylose reductase, xylitol dehydrogenase and xylulokinase genes, we compared the ability of this engineered strain to the benchmark 424A(LNH-ST) strain in ethanol production and xylose fermentation in standard lab medium and AFEX pretreated corn stover (ACS) hydrolysates, as well as in SSCF of ACS at different temperatures. In SSCF of 9% (w/w) glucan loading ACS at 35°C, the engineered strain showed higher cell viabilities and produced a similar amount of ethanol (51.3 g/L) compared to the benchmark 424A(LNH-ST) strain. These results validate our approach in the selection of wild Saccharomyces cerevisiae strains with thermo-tolerance and degradation products tolerance properties for lignocellulosic biofuel production. The wild and domesticated yeast strains phenotyped in this work are publically available for others to use as genetic backgrounds for fermentation of their pretreated biomass at elevated temperatures.