Screening of Trichoderma strains for maize straw degradation at low temperature

Abstract:

[Background] Species of Trichoderma are common cellulose and hemicellulose- degrading fungi in nature and play an important role in the degradation of agricultural wastes.[Objective] To screen out Trichoderma strains that can degrade maize straw under low temperature. [Methods] This study determined the growth rates and the diameter of hydrolytic transparent circle produced by cellulase and xylanase of 111 strains belonging to 31 Trichoderma species under low temperature, as well as the relative degradation rate (RDR) of the representative strains on maize straw. The cellulose filter paper enzyme (FPase), carboxymethyl cellulase (CMCase), and xylanase activities of the representative strains with different RDR values were determined by the DNS method, and the relationship between their enzyme activities and RDR in different fermentation stages were further analyzed. [Results] All the tested strains were able to grow at 15 ℃, whereas, 100 and 42 out of them could grow at 10 ℃ and 5 ℃, respectively. Among them, 19 strains produced hydrolytic both cellulose and xylan transparent circles with diameters more than 60 mm after 6 days, and their RDRs on maize straw after 10 days were 0.45%-8.09%. The activities of FPase, CMCase, and xylanase of the strains 9145, TC425, TC505, and 8987 showed a dynamic change with the cultivation time, of which the tendency of FPase and CMCase was basically identical and closely related to the RDR. [Conclusion] The strains of T. atrobrunneum, T. atroviride, T. hamatum, and T. simmonsii show high degradation rates of maize straw at low temperatures, which will provide germplasm resources for subsequent development of ripening agent, degradation mechanism research, and resource utilization of maize straw.

Key words:filamentous fungi;biodegradation;cellulase;xylanase;hydrolytic transparent circle;relative degradation rate