GICOM Research Group, Department of Chemical, Biological and Environmental Engineering, School of Engineering, Edifici Q, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain.
GICOM Research Group, Department of Chemical, Biological and Environmental Engineering, School of Engineering, Edifici Q, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain.
Sci Total Environ. 2017 Jul 1;589:56-65. doi: 10.1016/j.scitotenv.2017.02.184. Epub 2017 Mar 3.
The cost of cellulases is the main bottleneck for bioethanol production at commercial scale. Solid-state fermentation (SSF) is a promising technology that can potentially reduce cellulases cost by using wastes as substrates. In this work, a SSF system of 4.5L bioreactors was operated continuously by sequential batch operation using the fermented solids from one batch to inoculate the following batch. Coffee husk was used as lignocellulosic substrate. Compost was used as starter in the first batch to provide a rich microbiota. Two strategies were applied: using 10% fermented solids as inoculum in 48h batches (SB90) and using 50% solids in 24h batches (SB50). A consistent and robust production process was achieved by sequential batch operation. Similar cellulase activities around 10 Filter Paper Units per gram of dry solids were obtained through both strategies. Microbial diversity in the starting materials and in the final fermented solids was characterized by next generation sequencing. Microbial composition of both fermented solids was similar but the relative abundance of families and species was affected by the operation strategy used. Main bacteria in the final solids came from compost (families Sphingobacteriaceae, Paenibacillaceae and Xanthomonadaceae), while main fungi families came from coffee husk (families Phaffomycetaceae, Dipodascaceae and two unidentified families of the class of Tramellomycetes). There was a high presence of non-identified mycobiota in the fermented solids. Main identified species were the bacteria Pseudoxanthonomas taiwanensis (12.3% in SB50 and 6.1% in SB90) and Sphingobacterium composti (6.1% in SB50 and 2.6% in SB90) and the yeasts Cyberlindnera jardinii and Barnettozyma californica (17.8 and 4.1% respectively in SB50 and 34 and 9.1% in SB90), all four previously described as lignocellulose degraders. The development of these operational strategies and further biological characterization of the end product could eventually benefit the process economics by providing a standard and specialized inoculum for a continuous SSF for cellulases production.
纤维素酶的成本是纤维素酶生产达到商业规模的主要瓶颈。固态发酵（SSF）是一种很有前途的技术，它可以通过使用废物作为基质来降低纤维素酶的成本。在这项工作中，使用 4.5L 生物反应器的 SSF 系统通过连续分批操作进行连续运行，即用一批发酵的固体来接种下一批。咖啡壳被用作木质纤维素基质。在第一批中使用堆肥作为起始物，以提供丰富的微生物群。应用了两种策略：在 48 小时批次中使用 10%发酵固体作为接种物（SB90）和在 24 小时批次中使用 50%固体（SB50）。通过分批操作实现了一致和稳健的生产过程。通过两种策略都获得了约 10 个滤纸单位/克干固体的相似纤维素酶活性。通过下一代测序对起始材料和最终发酵固体中的微生物多样性进行了表征。两种发酵固体的微生物组成相似，但操作策略的使用影响了家族和物种的相对丰度。最终固体中的主要细菌来自堆肥（Sphingobacteriaceae、Paenibacillaceae 和 Xanthomonadaceae 家族），而主要真菌家族来自咖啡壳（Phaffomycetaceae、Dipodascaceae 和两个未鉴定的 Tramellomycetes 类真菌家族）。发酵固体中有很高比例的未鉴定真菌。主要鉴定的物种是细菌 Pseudoxanthonomas taiwanensis（SB50 中为 12.3%，SB90 中为 6.1%）和 Sphingobacterium composti（SB50 中为 6.1%，SB90 中为 2.6%）以及酵母 Cyberlindnera jardinii 和 Barnettozyma californica（SB50 中分别为 17.8%和 4.1%，SB90 中分别为 34%和 9.1%），这四种菌都被描述为木质纤维素降解菌。这些操作策略的发展和对最终产物的进一步生物学特性分析，最终可以通过为连续 SSF 生产纤维素酶提供标准和专用接种物来使该工艺的经济效益受益。
