Construction and evaluation of fungal consortia effect on maize straw degradation

Objectives The degradation of straw is relatively slow in nature due to its high content of complex celluloses. Increase in the degrading agents such as microbes and enzymatic activities may improve the degradation of straw. Thus, we studied the influence of microbial diversity and composition on maize straw degradation.

Methods Straw degrading fungi were isolated from the soil of maize straw field. Five fungi strains with high degradation ability were classified into microbial consortia through internal transcribed spacer (ITS) identification. The strain richness of the microbial consortia was set from 1 to 5 based on the degrading fungi. The relative degradation efficiency of maize straw and the activities of filter paper enzyme (FPe), CMCase and xylanase in different microbial consortia were assessed via variance and correlation analyses.

Results The five selected strains with high degradation efficiency were identified as Penicillium oxalicum Z7-6, Aspergillus fumigatus F7-5, Trichoderma harzianum F4-3, Irpex lacteus L1-1 and Fusarium equiseti J2-5 based on ITS alignment and phylogenic analysis. Relative straw degradation efficiency and cellulase activities of the fungal consortia were higher than single strains, and they increased with the enhancement of species richness in the fungal consortia. The consortia with strong activities of (FPe), CMCase and xylanase degraded maize straw more than others. FPe and CMCase strongly associated and contributed to relative degradation efficiency of the microbial consortia. Sampling effect analysis showed that different strains had different effects on maize straw degradation and cellulase activities. The maize straw degradation under all consortia without F7-5 strain was significantly higher than that with F7-5 strain. The fungal consortia of P. oxalicum Z7-6, T. harzianum F4-3, I. lacteus L1-1 and F. equiseti J2-5 showed the highest relative degradation efficiency and cellulase activities.

Conclusions Increasing the diversity of microbial consortia could enhance maize straw degradation; however, diversity and sampling effects should be considered during microbial composite construction.