Nitrogen amendment of green waste impacts microbial community, enzyme secretion and potential for lignocellulose decomposition

Abstract

Microorganisms involved in biomass deconstruction are an important resource for organic waste recycling and enzymes for lignocellulose bioconversion. The goals of this study were to examine the impact of nitrogen amendment on microbial community restructuring, secretion of xylanases and endoglucanases, and potential for biomass deconstruction. Communities were cultivated aerobically at 55 °C on green waste (GW) amended with varying levels of NH 4 Cl. Bacterial and fungal communities were determined using 16S rRNA and ITS region gene sequencing and PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) was applied to predict relative abundance of genes involved in lignocellulose hydrolysis. Nitrogen amendment significantly increased secretion of xylanases and endoglucanases, and microbial activity; enzyme activities and cumulative respiration were greatest when nitrogen level in GW was between 4.13-4.56 wt% (g/g), but decreased with higher nitrogen levels. The microbial community shifted to one with increasing potential to decompose complex polymers as nitrogen increased with peak potential occurring between 3.79-4.45 wt% (g/g) nitrogen amendment. The results will aid in informing the management of nitrogen level to foster microbial communities capable of secreting enzymes that hydrolyze recalcitrant polymers in lignocellulose and yield rapid decomposition of green waste.

Cultivation of black soldier fly larvae on almond byproducts: impacts of aeration and moisture on larvae growth and composition

“…Table lists the C/N ratio, moisture content, aeration rate, inoculation density of larvae and average larvae size for each experiment. The C/N ratio and moisture content ranges were selected because these were within the levels known to be ideal for the aerobic decomposition of plant residues by microorganisms …”

Effect of management of organic wastes on inactivation of Brassica nigra and Fusarium oxysporum f.sp. lactucae using soil biosolarization

“…They were mixed at a ratio (g/g dry basis) of 67:23 to achieve a C:N of 27. The green waste components included leaves, grass, prunings and trimmings, and branches and stumps, as described elsewhere . This composition was based on the California 2008 Statewide Waste Characterization Study .…”

The initial soil microbiota impacts the potential for lignocellulose degradation during soil solarization

“…; Yu et al . ), 51 were observed in the predicted metagenomes of the studied samples (Table ). To visualize the impact of SBS on the evolution of the selected lignocellulose degrading genes in the GW‐amended samples with or without compost, the correlation between their RA and time was calculated (Fig.…”

“…For predicted genes encoding hemicellulose degradation, seven of the nine genes that increased with SBS treatment time were found with RA >0·01% in the prior study (Yu et al . ). It is likely the presence of GW in the soil treatment system stimulated a community that harboured genes to degrade green‐waste derived cellulose, hemicellulose and lignin.…”

“…Among the currently collected and transported organic wastes, municipal green wastes (GW) are potential sources of organic carbon for SBS. Green waste can include mixtures of leaves, grass, prunings and trimmings, and branches and stumps (Yu et al 2017). The abilities of soil micro-organisms to rapidly adapt to the extreme conditions observed during SBS, such as fluctuating and elevated temperature and low oxygen concentrations, and to degrade lignocellulose are important to consider for SBS to compete with chemical fumigation.…”