• Energy Research

Abstract The microbial consortia designedly screened in our lab were used for solid-state pretreatment of tree trimmings to degrade lignin selectively in this work, and the commercial fungal isolate pretreatment was taken in comparison. The results showed that a highly selective degradation of lignin was observed in the tree trimmings pretreated via the microbial consortium DM-1, in which 14.0% of lignin was decomposed and no significant degradation of cellulose was noted within 20 days. Meanwhile, in this trial, shorter fibers and a lower crude fiber crystallinity were found in the tree trimmings after pretreatment. And the pH values of the tree trimmings undergoing biopretreatment in each trial were all kept at around 7.0. In the SSF (simultaneous saccharification and fermentation) process, 20% increment of the ethanol yield was obtained in the trial loaded with DM-1 pretreated tree trimmings compared to the control, in which a higher acid-based buffering capability was also observed. The scanning electron microscope test revealed that after SSF, the DM-1 pretreated tree trimmings had less crude fibers and more void ratios. Herein, it was feasible to produce more ethanol from tree trimmings via solid-state pretreatment by using the microbial consortium DM-1.

Pretreatment technologies that can not only reduce the recalcitrance of woody biomass but also achieve a high benefit-cost ratio are desirable for bioenergy production from woody biomass. In this study, an integrated process was proposed and conducted by pretreating woodchips via Shiitake cultivation for improved methane yield during solid-state anaerobic digestion (SS-AD), and simultaneously producing mushrooms as a high-value co-product. Shiitake cultivation using woodchips as the main substrate ingredient obtained mushroom yields comparable to those using a commercial substrate. Enzymatic digestibility and cumulative methane yields (133-160 L kg(-1)VS during 62 days of SS-AD) of pretreated substrates (spent mushroom substrate) were at least 1.5 times as high as those of untreated woodchips. Compared to a sole SS-AD process, the integrated Shiitake cultivation/SS-AD process increased methane production and solid waste reduction per kilogram of woodchips by about 1.5 and 8 times, respectively.