KOH-catalyzed synthesis of biodiesel was carried out in capillary microreactors with inner diameters of 0.25 or 0.53 mm, with unrefined rapeseed oil and cottonseed oil as raw materials. The influences of the methanol to oil molar ratio, the residence time, the catalyst concentration, the reaction temperature, and the dimension of the capillary on the production of biodiesel were examined. The results indicated that the residence time was greatly reduced by using microchannel reactors, compared with a conventional batch reactor. The reaction temperature was the minimal factor in the yield of methyl ester. Meanwhile, the methyl ester yield first increased with the methanol/oil ratio and then decreased due to emulsion and saponification. The inner diameter of the microchannel reactor had a strong influence on the transesterification reaction. Higher methyl ester yield could be obtained at shorter residence times for the microchannel reactor with the smaller inner diameter.

BackgroundThe genome of Schizophyllum commune encodes a diverse repertoire of degradative enzymes for plant cell wall breakdown. Recent comparative genomics study suggests that this wood decayer likely has a mode of biodegradation distinct from the well-established white-rot/brown-rot models. However, much about the extracellular enzyme system secreted by S. commune during lignocellulose deconstruction remains unknown and the underlying mechanism is poorly understood. In this study, extracellular proteins of S. commune colonizing Jerusalem artichoke stalk were analyzed and compared with those of two white-rot fungi Phanerochaete chrysosporium and Ceriporiopsis subvermispora and a brown-rot fungus Gloeophyllum trabeum.ResultsUnder solid-state fermentation (SSF) conditions, S. commune displayed considerably higher levels of hydrolytic enzyme activities in comparison with those of P. chrysosporium, C. subvermispora and G. trabeum. During biodegradation process, this fungus modified the lignin polymer in a way which was consistent with a hydroxyl radical attack, similar to that of G. trabeum. The crude enzyme cocktail derived from S. commune demonstrated superior performance over a commercial enzyme preparation from Trichoderma longibrachiatum in the hydrolysis of pretreated lignocellulosic biomass at low enzyme loadings. Secretomic analysis revealed that compared with three other fungi, this species produced a higher diversity of carbohydrate-degrading enzymes, especially hemicellulases and pectinases acting on polysaccharide backbones and side chains, and a larger set of enzymes potentially supporting the generation of hydroxyl radicals. In addition, multiple non-hydrolytic proteins implicated in enhancing polysaccharide accessibility were identified in the S. commune secretome, including lytic polysaccharide monooxygenases (LPMOs) and expansin-like proteins.ConclusionsPlant lignocellulose degradation by S. commune involves a hydroxyl radical-mediated mechanism for lignocellulose modification in parallel with the synergistic system of various polysaccharide-degrading enzymes. Furthermore, the complex enzyme system of S. commune holds significant potential for application in biomass saccharification. These discoveries will help unveil the diversity of natural lignocellulose-degrading mechanisms, and advance the design of more efficient enzyme mixtures for the deconstruction of lignocellulosic feedstocks.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0461-x) contains supplementary material, which is available to authorized users.

BackgroundMicrobial consortia represent promising candidates for aiding in the development of plant biomass conversion strategies for biofuel production. However, the interaction between different community members and the dynamics of enzyme complements during the lignocellulose deconstruction process remain poorly understood. We present here a comprehensive study on the community structure and enzyme systems of a lignocellulolytic microbial consortium EMSD5 during growth on corn stover, using metagenome sequencing in combination with quantitative metaproteomics.ResultsThe taxonomic affiliation of the metagenomic data showed that EMSD5 was primarily composed of members from the phyla Proteobacteria, Firmicutes and Bacteroidetes. The carbohydrate-active enzyme (CAZyme) annotation revealed that representatives of Firmicutes encoded a broad array of enzymes responsible for hemicellulose and cellulose deconstruction. Extracellular metaproteome analysis further pinpointed the specific role and synergistic interaction of Firmicutes populations in plant polysaccharide breakdown. In particular, a wide range of xylan degradation-related enzymes, including xylanases, β-xylosidases, α-l-arabinofuranosidases, α-glucuronidases and acetyl xylan esterases, were secreted by diverse members from Firmicutes during growth on corn stover. Using label-free quantitative proteomics, we identified the differential secretion pattern of a core subset of enzymes, including xylanases and cellulases with multiple carbohydrate-binding modules (CBMs). In addition, analysis of the coordinate expression patterns indicated that transport proteins and hypothetical proteins may play a role in bacteria processing lignocellulose. Moreover, enzyme preparation from EMSD5 demonstrated synergistic activities in the hydrolysis of pretreated corn stover by commercial cellulases from Trichoderma reesei.ConclusionsThese results demonstrate that the corn stover-adapted microbial consortium EMSD5 harbors a variety of lignocellulolytic anaerobic bacteria and degradative enzymes, especially those implicated in hemicellulose decomposition. The data in this study highlight the pivotal role and cooperative relationship of Firmicutes members in the biodegradation of plant lignocellulose by EMSD5. The differential expression patterns of enzymes reveal the strategy of sequential lignocellulose deconstruction by EMSD5. Our findings provide insights into the mechanism by which consortium members orchestrate their array of enzymes to degrade complex lignocellulosic biomass.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0658-z) contains supplementary material, which is available to authorized users.

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