Controlling microbial contamination during hydrolysis of AFEX-pretreated corn stover and switchgrass: effects on hydrolysate composition, microbial response and fermentation.
Controlling microbial contamination during hydrolysis of AFEX-pretreated corn stover and switchgrass: effects on hydrolysate composition, microbial response and fermentation.
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DOI：
10.1186/s13068-015-0356-2
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发表时间：
2015
影响因子：
6.3
通讯作者：
Zhang Y
中科院分区：
文献类型：
--
作者：
Serate J;Xie D;Pohlmann E;Donald C Jr;Shabani M;Hinchman L;Higbee A;Mcgee M;La Reau A;Klinger GE;Li S;Myers CL;Boone C;Bates DM;Cavalier D;Eilert D;Oates LG;Sanford G;Sato TK;Dale B;Landick R;Piotrowski J;Ong RG;Zhang Y
微生物转化木质纤维素原料为生物燃料仍然是生产可持续能源的有吸引力的手段。以一致的方式生产木质纤维素水解产物以研究不同原料水解产物中的微生物性能是至关重要的。由于未经处理的生物质或在工艺过程中的各个点可能会引入微生物污染，因此在水解产物生产过程中可能很难控制无菌性。在这项研究中，我们比较了AFEX预处理的玉米秸秆和柳枝稷的水解产物，使用两种不同的方法来控制污染：要么通过高压灭菌的预处理的原料酶水解之前，或通过引入抗生素的非高压灭菌的原料水解过程中。然后，我们进行了广泛的化学分析，化学基因组学和比较发酵，以评估用于生产玉米秸秆和柳枝稷水解产物的这两种不同方法之间的任何差异。高压灭菌预处理的原料可以消除各种原料的污染，而抗生素庆大霉素不能在水解过程中始终控制污染。与添加庆大霉素相比，水解前对生物质进行高压灭菌对矿物质浓度的影响很小，并且对这些水解物中发现的两种主要糖（葡萄糖和木糖）没有显着影响。然而，高压灭菌提高了一些呋喃和酚类化合物的浓度。使用酿酒酵母菌株的化学基因组学分析表明，在相同原料中使用这两种方法产生的AFEX预处理的水解产物之间具有高度相关性，表明高压灭菌和抗生素方法之间的差异极小。与S.酿酒酵母和运动发酵单胞菌也表明，高压灭菌AFEX预处理的原料对这些水解产物中的微生物性能没有显著影响。我们的研究结果表明，高压灭菌预处理的原料提供了优势，添加抗生素的水解产物的生产。高压灭菌方法产生的水解产物质量更一致，并且对微生物性能的影响也可以忽略不计。虽然通过在酶促水解之前对原料进行高压灭菌来提高一些木质纤维素降解抑制剂的水平，但是在使用两种不同方法产生的水解产物中的细菌或酵母发酵期间没有观察到对细胞生长、糖利用或乙醇生产的显著影响。本文的在线版本（doi：10.1186/s13068-015-0356-2）包含补充材料，可供授权用户使用。
Microbial conversion of lignocellulosic feedstocks into biofuels remains an attractive means to produce sustainable energy. It is essential to produce lignocellulosic hydrolysates in a consistent manner in order to study microbial performance in different feedstock hydrolysates. Because of the potential to introduce microbial contamination from the untreated biomass or at various points during the process, it can be difficult to control sterility during hydrolysate production. In this study, we compared hydrolysates produced from AFEX-pretreated corn stover and switchgrass using two different methods to control contamination: either by autoclaving the pretreated feedstocks prior to enzymatic hydrolysis, or by introducing antibiotics during the hydrolysis of non-autoclaved feedstocks. We then performed extensive chemical analysis, chemical genomics, and comparative fermentations to evaluate any differences between these two different methods used for producing corn stover and switchgrass hydrolysates. Autoclaving the pretreated feedstocks could eliminate the contamination for a variety of feedstocks, whereas the antibiotic gentamicin was unable to control contamination consistently during hydrolysis. Compared to the addition of gentamicin, autoclaving of biomass before hydrolysis had a minimal effect on mineral concentrations, and showed no significant effect on the two major sugars (glucose and xylose) found in these hydrolysates. However, autoclaving elevated the concentration of some furanic and phenolic compounds. Chemical genomics analyses using Saccharomyces cerevisiae strains indicated a high correlation between the AFEX-pretreated hydrolysates produced using these two methods within the same feedstock, indicating minimal differences between the autoclaving and antibiotic methods. Comparative fermentations with S. cerevisiae and Zymomonas mobilis also showed that autoclaving the AFEX-pretreated feedstocks had no significant effects on microbial performance in these hydrolysates. Our results showed that autoclaving the pretreated feedstocks offered advantages over the addition of antibiotics for hydrolysate production. The autoclaving method produced a more consistent quality of hydrolysate, and also showed negligible effects on microbial performance. Although the levels of some of the lignocellulose degradation inhibitors were elevated by autoclaving the feedstocks prior to enzymatic hydrolysis, no significant effects on cell growth, sugar utilization, or ethanol production were seen during bacterial or yeast fermentations in hydrolysates produced using the two different methods. The online version of this article (doi:10.1186/s13068-015-0356-2) contains supplementary material, which is available to authorized users.