Caputo Fabio, Siaperas Romanos, Dias Camila, Nikolaivits Efstratios, Olsson Lisbeth
Division of Industrial Biotechnology, Department of Life Sciences, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden.
Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Heroon Polytechniou 9, 15772, Athens, Greece.
Biotechnol Biofuels Bioprod. 2024 Oct 5;17(1):127. doi: 10.1186/s13068-024-02569-3.
The efficient use of softwood in biorefineries is hampered by its recalcitrance to enzymatic saccharification. In the present study, the fungus Thermothielavioides terrestris LPH172 was cultivated on three steam-pretreated spruce materials (STEX, STEX, and STEX), characterized by different hemicellulose content and structure, as well as on untreated biomass. The aim of the study was to map substrate-induced changes in the secretome of T. terrestris grown on differently treated spruce materials and to evaluate the hydrolytic efficiency of the secretome as supplement for a commercial enzyme mixture.
The cultivation of T. terrestris was monitored by endo-cellulase, endo-xylanase, endo-mannanase, laccase, and peroxidase activity measurements. Proteomic analysis was performed on the secretomes induced by the spruce materials to map the differences in enzyme production. Growth of T. terrestris on STEX and STEX induced higher expression level of mannanases and mannosidases of the GH5_7 CAZy family compared to cultivation on the other materials. Cultivation on untreated biomass led to overexpression of GH47, GH76, and several hemicellulose debranching enzymes compared to the cultivation on the pretreated materials. T. terrestris grown on untreated, STEX and STEX induced three arabinofuranosidases of the GH43 and GH62 families; while growth on STEX induced a GH51 arabinofuranosidase and a GH115 glucuronidase. All secretomes contained five lytic polysaccharide monooxygenases of the AA9 family. Supplementation of Celluclast® + Novozym188 with the secretome obtained by growing the fungus grown on STEX achieved a twofold higher release of mannose from spruce steam-pretreated with acetic acid as catalyst, compared to the commercial enzyme cocktail alone.
Minor changes in the structure and composition of spruce affect the composition of fungal secretomes, with differences in some classes explaining an increased hydrolytic efficiency. As demonstrated here, saccharification of spruce biomass with commercial enzyme cocktails can be further enhanced by supplementation with tailor-made secretomes.
软木在生物精炼厂中的有效利用受到其对酶促糖化抗性的阻碍。在本研究中，将土栖嗜热丝孢菌LPH172接种于三种经蒸汽预处理的云杉材料（STEX、STEX和STEX）上进行培养，这些材料具有不同的半纤维素含量和结构，同时也接种于未处理的生物质上。本研究的目的是描绘在不同处理的云杉材料上生长的土栖嗜热丝孢菌分泌组中底物诱导的变化，并评估该分泌组作为商业酶混合物补充剂的水解效率。
通过内切纤维素酶、内切木聚糖酶、内切甘露聚糖酶、漆酶和过氧化物酶活性测定来监测土栖嗜热丝孢菌的培养情况。对云杉材料诱导的分泌组进行蛋白质组分析，以描绘酶产生的差异。与在其他材料上培养相比，土栖嗜热丝孢菌在STEX和STEX上生长诱导了GH5_7糖基水解酶家族的甘露聚糖酶和甘露糖苷酶更高的表达水平。与在预处理材料上培养相比，在未处理的生物质上培养导致GH47、GH76和几种半纤维素去分支酶的过表达。土栖嗜热丝孢菌在未处理的、STEX和STEX上生长诱导了GH43和GH62家族的三种阿拉伯呋喃糖苷酶；而在STEX上生长诱导了一种GH51阿拉伯呋喃糖苷酶和一种GH115葡糖醛酸酶。所有分泌组都含有AA9家族的五种裂解多糖单加氧酶。与单独使用商业酶混合物相比，用在STEX上生长的真菌获得的分泌组补充Celluclast® + Novozym188，从以乙酸为催化剂进行蒸汽预处理的云杉中释放的甘露糖增加了两倍。
云杉结构和组成的微小变化会影响真菌分泌组的组成，某些类别的差异解释了水解效率的提高。如此处所示，通过补充定制的分泌组可以进一步提高商业酶混合物对云杉生物质的糖化作用。
