【作者】 张翼；

【导师】 鲍杰； 乔庆安；

【作者基本信息】 华东理工大学 ， 生物工程（专业学位）， 2021， 硕士

【摘要】 预处理是破坏木质纤维素的致密结构进而促进后续酶解的关键步骤。预处理过程中产生的抑制物导致微生物难以在木质纤维素体系中生存,因此通过脱毒处理去除抑制物是进行高效油脂发酵的前提。生物脱毒是一种极具优势的脱毒方式,它能够在有效保留可发酵单糖的前提下,选择性地去除弱有机酸和呋喃醛类抑制物;然而生物脱毒法去除酚醛抑制物的效率较低。以往的研究结果表明,即使通过生物脱毒法对原料进行了深度解毒,大部分油脂酵母仍然不能在木质纤维素原料中存活。本文首先探究了各类油脂酵母在经过生物脱毒的木质纤维素原料中生长和代谢状况;我们猜测残留的酚醛抑制物可能导致了其细胞生长和代谢不良的现象,并对此猜测进行了验证。在仅含酚醛抑制物的合成培养基和麦秆水解液中,圆红冬孢酵母(Rhodosporidium toruloides),粘红酵母(Rhodotorulaglutinis),解脂耶氏酵母(Yarrowia lipolytica)几乎不能生长,两株皮状丝孢酵母(Trichosporon cutaneum ACCC 20271,Trichosporon cutaneum MP11)的细胞生长和油脂积累也受到明显影响,表明酚醛类抑制物的存在是导致油脂酵母在木质纤维素体系中生长和代谢不良的主要原因。其次探究了上述5株酵母对三种典型酚醛抑制物的转化能力,皮状丝孢酵母可以将4-羟基苯甲醛(HBA)、香草醛或丁香醛完全转化为它们的醇、酸衍生物,然后进一步降解酸;其它三株酵母仅能将少量的酚醛转化为它们的醇、酸衍生物,不能进一步降解酸。最后以小麦秸秆为原料在高固含量下进行了同步糖化与共发酵,结果表明皮状丝孢酵母在实际体系中的油脂发酵可以获得良好的油脂产量(40.87±1.85 g/L)。上述结果为皮状丝孢酵母在纤维素油脂生产上的应用提供了重要的理论依据。此外,本文还探究了皮状丝孢酵母对木质纤维素主要抑制物乙酸和乙酰丙酸的利用情况。以乙酸和乙酰丙酸为碳源进行分批补料发酵,皮状丝孢酵母T.cutaneum MP11能利用乙酸和乙酰丙酸进行生长和油脂积累,为木质纤维素来源的非常规碳源的利用提供了依据。更多还原

【Abstract】 Pretreatment is the key step to destroy the dense structure of lignocellulose and promote the subsequent enzymatic hydrolysis.However,microorganisms are generally hard to survive in lignocellulose system due to the presence of inhibitors generated from the lignocellulose pretreatment,so the detoxification step is always followed to remove the inhibitors.Biodetoxification have great advantages on the removal of inhibitors,which can selectively remove weak organic acids and furan aldehydes inhibitors without causing the loss of fermentable sugars;However,biodetoxification has a low efficiency in removing phenolic inhibitors.Previous results show that many oleaginous yeasts are difficult to survive in lignocellulosic feedstock,even the raw materials have been deeply detoxified by biodetoxification.This study firstly investigated the cell growth and metabolism of various oleaginous yeasts in the pretreated and biodetoxified lignocellulosic feedstock.It is suspected that the existence of residual phenolic aldehydes is responsible for the poor viability of oleaginous yeasts.While cultured in the synthetic medium containing only phenolic aldehydes inhibitors and wheat straw hydrolysate,Rhodosporidium toruloides,Rhodotorula glutinis,Yarrowia lipolytica are generally hard to survive;the cell growth and lipid accumulation of T.cutaneum ACCC 20271,T.cutaneum MP11 were also significantly affected.These results confirmed that the existence of residual phenolic aldehydes was the major reason for poor cell growth and metabolism of oleaginous yeasts in lignocellulosic feedstock.Secondly,the bioconversion of phenolic aldehydes by the above 5 strains of yeast was investigated.T.cutaneum ACCC 20271 and T.cutaneum MP11 almost completely converted 4-hydroxybenzaldehyde(HBA),vanillin or syringaldehyde into their alcohols and acids form,then alcohol or acid were also effectively degraded;on the other hand,the other three yeasts can only convert a small amount of 4-hydroxybenzaldehyde,vanillin or syringaldehyde into alcohol and acid derivatives,and the acid can’t be further degraded.Finally,simultaneous saccharification and lipid co-fermentation was carried out using wheat straw under high solid content,T.cutaneum showed satisfactory lipid accumulation in the actual system(40.87±1.85 g/L).These results provide an important theoretical basis for the application of T.cutaneum to the lipid production from lignocellulose.In addition,the utilization of acetic acid and levulinic acid by T.cutaneum,which were main weak organic acids inhibitors from lignocellulose,was also investigated.By using acetic acid and levulinic acid as carbon sources for fed-batch fermentation,T.cutaneum MP11 can use acetic acid and levulinic acid for cell growth and lipid accumulation.This study provides a theoretical support for the utilization of unconventional carbon sources from lignocellulose.更多还原