Hyperoxic Gas Conditioning Enhanced Microbial Wood Degradation in a Meso-thermophilic Composting Environment

Compost heat recovery holds promise in harnessing wood energy for sustainable and low-temperature decentralized heating. Here, we present the first application of hyperoxic gas conditioning (HGC), in which the oxygen concentration in the incubation atmosphere is elevated above 20%, to regulate microbial wood degradation in a composting environment. Wood degradation performance by undefined meso-thermophilic fungal-bacterial consortia was investigated under three gaseous oxygen concentrations: control (10-20%, O20), moderately hyperoxic (30-50%, O50), and highly hyperoxic (60-80%, O80). Both hyperoxic gas treatments increased total wood dry mass loss after 60 days, as well as oxygen consumption rates during the later stages of incubation. O50 achieved the highest wood degradation in terms of dry matter, lignin, and carbohydrates, and was accompanied by the greatest MnP and laccase activities and increased fungal diversity and abundance of Basidiomycota. O80, in contrast, led to the lowest lignin removal, laccase activity, and microbial richness, likely due to excessive long-term oxidative stress. This study demonstrates for the first time that HGC can improve overall wood degradation during composting by modulating the composition of meso-thermophilic fungi and bacteria and their associated enzyme activities, offering a strategy to steer and optimize aerobic lignocellulose bioconversion in open mixed-culture systems.