Programa de Processos Tecnológicos e Ambientais, Universidade de Sorocaba, Sorocaba, Brazil.
Manchester Institute of Biotechnology, Department of Chemistry, University of Manchester, Manchester, United Kingdom.
Appl Environ Microbiol. 2020 Sep 1;86(18). doi: 10.1128/AEM.00199-20.
Lignocellulose is one of the most abundant renewable carbon sources, representing an alternative to petroleum for the production of fuel and chemicals. Nonetheless, the lignocellulose saccharification process, to release sugars for downstream applications, is one of the most crucial factors economically challenging to its use. The synergism required among the various carbohydrate-active enzymes (CAZymes) for efficient lignocellulose breakdown is often not satisfactorily achieved with an enzyme mixture from a single strain. To overcome this challenge, enrichment strategies can be applied to develop microbial communities with an efficient CAZyme arsenal, incorporating complementary and synergistic properties, to improve lignocellulose deconstruction. We report a comprehensive and deep analysis of an enriched rumen anaerobic consortium (ERAC) established on sugarcane bagasse (SB). The lignocellulolytic abilities of the ERAC were confirmed by analyzing the depolymerization of bagasse by scanning electron microscopy, enzymatic assays, and mass spectrometry. Taxonomic analysis based on 16S rRNA sequencing elucidated the community enrichment process, which was marked by a higher abundance of and species. Shotgun metagenomic sequencing of the ERAC disclosed 41 metagenome-assembled genomes (MAGs) harboring cellulosomes and polysaccharide utilization loci (PULs), along with a high diversity of CAZymes. The amino acid sequences of the majority of the predicted CAZymes (60% of the total) shared less than 90% identity with the sequences found in public databases. Additionally, a clostridial MAG identified in this study produced proteins during consortium development with scaffoldin domains and CAZymes appended to dockerin modules, thus representing a novel cellulosome-producing microorganism. The lignocellulolytic ERAC displays a unique set of plant polysaccharide-degrading enzymes (with multimodular characteristics), cellulosomal complexes, and PULs. The MAGs described here represent an expansion of the genetic content of rumen bacterial genomes dedicated to plant polysaccharide degradation, therefore providing a valuable resource for the development of biocatalytic toolbox strategies to be applied to lignocellulose-based biorefineries.
木质纤维素是最丰富的可再生碳源之一，是生产燃料和化学品的石油替代品。然而，木质纤维素的糖化过程（即释放用于下游应用的糖）是其经济应用最关键的因素之一。为了有效地分解木质纤维素，各种碳水化合物活性酶（CAZymes）之间需要协同作用，但单一菌株的酶混合物往往无法令人满意地实现这种协同作用。为了克服这一挑战，可以应用富集策略来开发具有有效 CAZyme 武器库的微生物群落，其中包含互补和协同的特性，以改善木质纤维素的解构。我们报告了对基于甘蔗渣（SB）建立的富集瘤胃厌氧群落（ERAC）的全面和深入分析。通过扫描电子显微镜分析、酶测定和质谱分析，证实了 ERAC 的木质纤维素分解能力。基于 16S rRNA 测序的分类分析阐明了群落的富集过程，其中 和 物种的丰度更高。ERAC 的鸟枪法宏基因组测序揭示了 41 个含有纤维小体和多糖利用基因座（PULs）的宏基因组组装基因组（MAGs），以及丰富的 CAZymes。预测的 CAZymes 的大部分氨基酸序列（占总数的 60%）与公共数据库中的序列的相似度小于 90%。此外，本研究中鉴定的梭菌 MAG 在群落发展过程中产生了具有支架结构域和 CAZymes 附加到 dockerin 模块的蛋白质，因此代表了一种新型的产纤维小体微生物。木质纤维素分解的 ERAC 显示了一组独特的植物多糖降解酶（具有多模块特性）、纤维小体复合物和 PULs。本文描述的 MAG 扩展了专门用于植物多糖降解的瘤胃细菌基因组的遗传内容，因此为基于木质纤维素的生物炼制厂应用的生物催化工具箱策略的开发提供了有价值的资源。
