Integrated management of hemicellulosic fraction and its economical transformation to value-added products is the key driver towards sustainable lignocellulosic biorefineries. In this aspect, microbial cell factories are harnessed for the sustainable production of commercially viable biochemicals by valorising C5 and C6 sugars generated from agro-industrial waste. However, in the terrestrial ecosystem, microbial systems can efficiently consume glucose. On the contrary, pentose sugars are less preferred carbon source as most of the microbes lack metabolic pathway for their utilization. The effective utilization of both pentose and hexose sugars is key for economical biorefinery. Bioprospecting the food waste and selective enrichment on xylose-rich medium led to screening and isolation of yeast which was phylogenetically identified as Pichia fermentans. The newly isolated xylose assimilating yeast was explored for xylitol production. The wild type strain robustly grew on xylose and produced xylitol with > 40% conversion yield. Chemical mutagenesis of isolated yeast with ethyl methanesulphonate (EMS) yielded seven mutants. The mutant obtained after 15 min EMS exposure, exhibited best xylose bioconversion efficiency. This mutant under shake flask conditions produced maximum xylitol titer and yield of 34.0 g/L and 0.68 g/g, respectively. However, under the same conditions, the control wild type strain accumulated 27.0 g/L xylitol with a conversion yield of 0.45 g/g. Improved performance of the mutant was attributed to 34.6% activity enhancement in xylose reductase with simultaneous reduction of xylitol dehydrogenase activity by 22.9%. Later, the culture medium was optimized using statistical design and validated at shake flask and bioreactor level. Bioreactor studies affirmed the competence of the mutant for xylitol accumulation. The xylitol titer and yield obtained with pure xylose were 98.9 g/L and 0.67 g/g, respectively. In comparison, xylitol produced using non-detoxified xylose rich pre-hydrolysate from sugarcane bagasse was 79.0 g/L with an overall yield of 0.54 g/g. This study demonstrates the potential of newly isolated P. fermentans in successfully valorising the hemicellulosic fraction for the sustainable xylitol production.

中文翻译：

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使用新分离的毕赤酵母发酵罐，利用甘蔗渣中未解毒的富含木糖的预水解物提高木糖醇的生产

半纤维素馏分的综合管理及其向增值产品的经济转型，是实现可持续木质纤维素生物精炼厂的关键动力。在这方面，微生物细胞工厂被利用来通过农产品工业废物产生的C5和C6糖的增值来可持续地生产商业上可行的生物化学药品。但是，在陆地生态系统中，微生物系统可以有效地消耗葡萄糖。相反，戊糖是次要的碳源，因为大多数微生物缺乏利用它们的代谢途径。有效利用戊糖和己糖是经济型生物精炼的关键。对食物浪费进行生物勘探并在富含木糖的培养基上进行选择性富集，导致了对酵母的筛选和分离，该酵母在系统发育上被鉴定为发酵毕赤酵母。探索新分离的木糖同化酵母以生产木糖醇。野生型菌株在木糖上强劲生长，并以> 40％的转化率产生木糖醇。用甲烷磺酸乙酯（EMS）对分离的酵母进行化学诱变产生了七个突变体。EMS暴露15分钟后获得的突变体表现出最佳的木糖生物转化效率。在摇瓶条件下，该突变体产生最大的木糖醇滴度，产率分别为34.0g / L和0.68g / g。然而，在相同条件下，对照野生型菌株积累了27.0g / L的木糖醇，转化率为0.45g / g。该突变体的性能提高归因于34。木糖还原酶的活性提高6％，同时木糖醇脱氢酶活性降低22.9％。之后，使用统计设计对培养基进行优化，并在摇瓶和生物反应器一级进行验证。生物反应器研究证实了该突变体对木糖醇积累的能力。用纯木糖得到的木糖醇效价和产率分别为98.9g / L和0.67g / g。相比之下，使用甘蔗渣中未解毒的富含木糖的预水解产物生产的木糖醇为79.0 g / L，总产量为0.54 g / g。这项研究表明，新分离的发酵发酵单胞菌具有潜力，可以成功地使半纤维素部分增值，从而实现可持续的木糖醇生产。使用统计设计优化培养基，并在摇瓶和生物反应器一级进行验证。生物反应器研究证实了该突变体对木糖醇积累的能力。用纯木糖得到的木糖醇效价和产率分别为98.9g / L和0.67g / g。相比之下，使用甘蔗渣中未解毒的富含木糖的预水解产物生产的木糖醇为79.0 g / L，总产量为0.54 g / g。这项研究表明，新分离的发酵发酵单胞菌具有潜力，可以成功地使半纤维素部分增值，从而实现可持续的木糖醇生产。使用统计设计优化培养基，并在摇瓶和生物反应器一级进行验证。生物反应器研究证实了该突变体对木糖醇积累的能力。用纯木糖得到的木糖醇效价和产率分别为98.9g / L和0.67g / g。相比之下，使用甘蔗渣中未解毒的富含木糖的预水解产物生产的木糖醇为79.0 g / L，总产量为0.54 g / g。这项研究表明，新分离的发酵发酵单胞菌具有潜力，可以成功地使半纤维素部分增值，从而实现可持续的木糖醇生产。分别为67g / g。相比之下，使用甘蔗渣中未解毒的富含木糖的预水解产物生产的木糖醇为79.0 g / L，总产量为0.54 g / g。这项研究表明，新分离的发酵发酵单胞菌具有潜力，可以成功地使半纤维素部分增值，从而实现可持续的木糖醇生产。分别为67g / g。相比之下，使用甘蔗渣中未解毒的富含木糖的预水解产物生产的木糖醇为79.0 g / L，总产量为0.54 g / g。这项研究表明，新分离的发酵发酵单胞菌具有潜力，可以成功地使半纤维素部分增值，从而实现可持续的木糖醇生产。