The use of lytic polysaccharide monooxygenases in anaerobic digestion of lignocellulosic materials

Abstract

BackgroundThe recent discovery that LPMOs can work under anaerobic conditions when supplied with low amounts H2O2 opens the possibility of using LPMOs as enzyme aids in biogas reactors to increase methane yields from lignocellulosic materials. We have explored this possibility by studying anaerobic digestion of various lignocellulosic materials: Avicel, milled spruce and birch wood, and a lignin-rich hydrolysis residue from steam-exploded birch. The digestions were added LPMOs and various cellulolytic enzyme cocktails and were carried out with or without addition of H2O2.ResultsIn several cases, enzyme addition had a beneficial effect on methane production, which was partly due to components present in the enzyme preparations. It was possible to detect LPMO activity during the initial phases of the anaerobic digestions of Avicel, and in some cases LPMO activity could be correlated with improved methane production from lignocellulosic materials. However, a positive effect on methane production was only seen when LPMOs were added together with cellulases, and never upon addition of LPMOs only. Generally, the experimental outcomes showed substrate-dependent variations in process efficiency and the importance of LPMOs and added H2O2. These differences could relate to variations in the type and content of lignin, which again will affect the activity of the LPMO, the fate of the added H2O2 and the generation of potentially damaging reactive-oxygen species. The observed effects showed that the interplay between cellulases and LPMOs is important for the overall efficiency of the process.ConclusionThis study shows that it may be possible to harness the power of LPMOs in anaerobic digestion processes and improve biogas production, but also highlight the complexity of the reaction systems at hand. One complicating factor was that the enzymes themselves and other organic components in the enzyme preparations acted as substrates for biogas production, meaning that good control reactions were essential to detect effects caused by enzyme activity. As also observed during regular aerobic enzymatic digestion of lignocellulosic biomass, the type and contents of lignin in the substrates likely plays a major role in determining the impact of LPMOs and of cellulolytic enzymes in general. More work is needed to unravel the interplay between LPMOs, O2, H2O2, and the multitude of redox-active components found in anaerobic bioreactors degrading lignocellulosic substrates.

Comparative Genomic Analysis of Dactylonectria torresensis Strains from Grapevine, Soil and Weed Highlights Potential Mechanisms in Pathogenicity and Endophytic Lifestyle

“…Cellulose dehydrogenases (CDHs) of the family AA3-1 are known to reduce LPMOs in nature and are hence crucial for their function [ 73 ]. Hence, the combination of these LPMOs and CDHs along with the fact that LPMOs were also found to be efficient under anaerobic conditions [ 74 ], make them ideal candidates for virulence factors of Dactylonectria .…”

Stimulating Biogas Production from Steam-Exploded Birch Wood Using Fenton Reaction and Fungal Pre-Treatment

“…They reported a maximum methane production yield of 196 mL/gvS . Costa et al (2019) employed several hydrolysis enzymes and H 2 O 2 together with the SEBW to assess the methane production yield. They reported a methane yield improvement from 110 mL/gvS in samples with only birch wood to over 200 mL/gvS in samples with enzyme and H 2 O 2 (Costa et al, 2019).…”

“…Costa et al (2019) employed several hydrolysis enzymes and H 2 O 2 together with the SEBW to assess the methane production yield. They reported a methane yield improvement from 110 mL/gvS in samples with only birch wood to over 200 mL/gvS in samples with enzyme and H 2 O 2 (Costa et al, 2019). Matsakas et al (2020) employed a combined organosol-SE for the pretreatment of birch wood.…”

Improving The Biodegradability of Rice Straw by Electrochemical Pretreatment

“…A negative control was also conducted using HPW instead of chemical solutions. Blank control (inoculum only) was not conducted because the biogas production from inoculum is negligible [41,42].…”