Degradation of unpretreated wheat straw by Caldicellulosiruptor saccharolyticus F32 and its enzyme characteristics

Abstract:

[Objective] This study is aimed to characterize fermentation and enzyme characteristics of an extremely thermophilic anaerobic lignocellulolytic bacterium Caldicellulosiruptor saccharolyticus F32. [Methods] Cell growth was monitored by cell counting. Acetate, lactate and residual reducing sugars were measured by using an ion chromatography system. H2 was detected by gas chromatography. DNS method and p-nitrophenyl method were used to measure the enzyme activities of the secreted proteins of C. saccharolyticus F32 and DSM 8903. [Results] In contrast to C. saccharolyticus DSM 8903, strain F32 grew better on cellulose (Avicel PH-101), even on unpretreated wheat straw. Compared to C. saccharolyticus DSM 8903, strain F32 produced more lactate as the end product, thereby decreasing the hydrogen yield when glucose was used as carbon source. The secretome of strain F32 showed higher endoglucanase and xylanase activities. [Conclusion] In comparison with C. saccharolyticus DSM 8903, C. saccharolyticus F32 could degrade lignocellulosic biomass more efficiently. There were significant difference in the products, cellulase and hemicellulase systems between C. saccharolyticus F32 and C. saccharolyticus DSM 8903.

Key words:Trametes pubescens pellets, Continuous addition of dye, Degraded metabolites characterization, Phytotoxicity