Department of Hydraulics and Sanitation, School of Engineering of São Carlos, University of São Paulo (USP), Av. Trabalhador São Carlense, 400, 13566-590, São Carlos, SP, Brazil.
Department of Biology, Federal University of São Carlos (UFSCar), João Leme dos Santos Highway, Km 101, zipcode 18052-780, Sorocaba, São Paulo, Brazil.
J Environ Manage. 2021 Aug 1;291:112631. doi: 10.1016/j.jenvman.2021.112631. Epub 2021 Apr 28.
Energy recovery from lignocellulosic waste has been studied as an alternative to the problem of inappropriate waste disposal. The present study aimed at characterizing the microbial community and the functional activity of reactors applied to H production through lignocellulosic waste fermentation in optimized conditions. The latter were identified by means of Rotational Central Composite Design (RCCD), applied to optimize allochthonous inoculum concentration (2.32-5.68 gTVS/L of granular anaerobic sludge), pH (4.32-7.68) and Citrus Peel Waste (CPW) concentration (1.55-28.45 g/L). After validation, the conditions identified for optimal H production were 4 gSTV/L of allochthonous inoculum, 29.8 g/L of CPW (substrate) and initial pH of 8.98. In these conditions, 48.47 mmol/L of H was obtained, which is 3.64 times higher than the concentration in unoptimized conditions (13.31 mmol H/L using 15 g/L of CPW, 2 gTVS/L of allochthonous inoculum, pH 7.0). Acetogenesis was the predominant pathway, and maximal concentrations of 3,731 mg/L of butyric acid and 3,516 mg/L of acetic acid were observed. Regarding the metataxonomic profile, Clostridium genus was dramatically favored in the optimized condition (79.78%) when compared to the allochthonous inoculum (0.43%). It was possible to identify several genes related to H (i.e dehydrogenases) and volatile fatty acids (VFA) production and with cellulose degradation, especially some CAZymes from the classes Auxiliary Activities, Glycoside Hydrolases and Glycosyl Transferase. By means of differential gene expression it was observed that cellulose degradation and acetic acid production pathways were overabundant in samples from the optimized reactors, highlighting endo-β-1,4-glucanase/cellulose, endo-β-1,4-xylanase, β-glucosidase, β-mannosidase, cellulose β-1,4-cellobiosidase, cellobiohydrolase, and others, as main the functions.
从木质纤维素废物中回收能源已被研究为解决不当废物处理问题的一种替代方法。本研究旨在通过优化条件下木质纤维素废物发酵生产氢气，对应用于氢气生产的反应器中的微生物群落和功能活性进行特征描述。通过旋转中心复合设计（RCCD）对后者进行了鉴定，该设计应用于优化异源接种物浓度（2.32-5.68 gTVS/L 颗粒厌氧污泥）、pH 值（4.32-7.68）和柑橘皮废物（CPW）浓度（1.55-28.45 g/L）。验证后，确定最佳产氢条件为异源接种物 4 gSTV/L、CPW（底物）29.8 g/L 和初始 pH 值 8.98。在此条件下，获得了 48.47 mmol/L 的 H，是未优化条件下浓度（使用 15 g/L CPW、2 gTVS/L 异源接种物、pH 值 7.0 时获得 13.31 mmol H/L）的 3.64 倍。乙酰生成是主要途径，丁酸的最大浓度为 3731mg/L，乙酸的最大浓度为 3516mg/L。关于分类组学概况，与异源接种物（0.43%）相比，在优化条件下梭菌属（Clostridium）的比例明显较高（79.78%）。可以鉴定出与 H（即脱氢酶）和挥发性脂肪酸（VFA）生产以及纤维素降解相关的几个基因，特别是一些辅助活性、糖苷水解酶和糖基转移酶类的 CAZymes。通过差异基因表达观察到，优化反应器中的样品中纤维素降解和乙酸生产途径丰富，突出了内切-β-1,4-葡聚糖酶/纤维素、内切-β-1,4-木聚糖酶、β-葡萄糖苷酶、β-甘露糖苷酶、纤维素 β-1,4-纤维二糖酶、纤维二糖水解酶等，这些酶是主要的功能酶。
