Xiros Charilaos, Studer Michael H
Laboratory for Bioenergy and Biochemicals, School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Bern, Switzerland.
Front Microbiol. 2017 Oct 10;8:1930. doi: 10.3389/fmicb.2017.01930. eCollection 2017.
The constraints and advantages in cellulolytic enzymes production by fungal biofilms for a consolidated bioconversion process were investigated during this study. The biofilm cultivations were carried out in reactors designed for consolidated bioprocessing Multispecies Biofilm Membrane reactors, (MBM) where an aerobic fungal biofilm produces the lignocellulolytic enzymes while a fermenting microorganism forms the fermentation product at anaerobic conditions. It was shown that although mycelial growth was limited in the MBM reactors compared to submerged cultivations, the secretion of cellulolytic enzymes per cell dry weight was higher. When was used as the sole enzyme producer, cellobiose accumulated in the liquid medium as the result of the deficiency of -glucosidase in the fungal secretome. To enhance -glucosidase activity, was co-cultivated with which is a -glucosidase overproducer. The two fungi formed a multispecies biofilm which produced a balanced cellulolytic cocktail for the saccharification of plant biomass. The mixed biofilm reached a 2.5 fold increase in -glucosidase production, compared to the single biofilm. The enzymatic systems of single and mixed biofilms were evaluated regarding their efficiency on cellulosic substrates degradation. Washed solids from steam pretreated beechwood, as well as microcrystalline cellulose were used as the substrates. The enzymatic system of the multispecies biofilm released four times more glucose than the enzymatic system of alone from both substrates and hydrolyzed 78 and 60% of the cellulose content of washed solids from beechwood and microcrystalline cellulose, respectively.
在本研究中，对真菌生物膜生产纤维素分解酶用于联合生物转化过程中的限制因素和优势进行了研究。生物膜培养在为联合生物处理设计的多物种生物膜膜反应器（MBM）中进行，其中需氧真菌生物膜产生木质纤维素分解酶，而发酵微生物在厌氧条件下形成发酵产物。结果表明，尽管与深层培养相比，MBM反应器中的菌丝体生长受到限制，但每单位细胞干重的纤维素分解酶分泌量更高。当仅使用一种酶产生菌时，由于真菌分泌组中缺乏β -葡萄糖苷酶，纤维二糖在液体培养基中积累。为了提高β -葡萄糖苷酶活性，将一种酶产生菌与一种β -葡萄糖苷酶高产菌共同培养。这两种真菌形成了一种多物种生物膜，该生物膜产生了用于植物生物质糖化的平衡纤维素分解酶混合物。与单一酶产生菌的生物膜相比，混合生物膜的β -葡萄糖苷酶产量提高了2.5倍。对单一和混合生物膜的酶系统在纤维素底物降解效率方面进行了评估。蒸汽预处理山毛榉木的洗涤固体以及微晶纤维素用作底物。多物种生物膜的酶系统从两种底物中释放的葡萄糖比单一酶产生菌的酶系统多四倍，并且分别水解了山毛榉木洗涤固体和微晶纤维素中78%和60%的纤维素含量。
