Enhanced biomethane production rate and yield from lignocellulosic ensiled forage ley by in situ anaerobic digestion treatment with endogenous cellulolytic enzymes

Abstract

BackgroundEnzymatic treatment of lignocellulosic material for increased biogas production has so far focused on pretreatment methods. However, often combinations of enzymes and different physicochemical treatments are necessary to achieve a desired effect. This need for additional energy and chemicals compromises the rationale of using enzymes for low energy treatment to promote biogas production. Therefore, simpler and less energy intensive in situ anaerobic digester treatment with enzymes is desirable. However, investigations in which exogenous enzymes are added to treat the material in situ have shown mixed success, possibly because the enzymes used originated from organisms not evolutionarily adapted to the environment of anaerobic digesters. In this study, to examine the effect of enzymes endogenous to methanogenic microbial communities, cellulolytic enzymes were instead overproduced and collected from a dedicated methanogenic microbial community. By this approach, a solution with very high endogenous microbial cellulolytic activity was produced and tested for the effect on biogas production from lignocellulose by in situ anaerobic digester treatment.ResultsAddition of enzymes, endogenous to the environment of a mixed methanogenic microbial community, to the anaerobic digestion of ensiled forage ley resulted in significantly increased rate and yield of biomethane production. The enzyme solution had an instant effect on more readily available cellulosic material. More importantly, the induced enzyme solution also affected the biogas production rate from less accessible cellulosic material in a second slower phase of lignocellulose digestion. Notably, this effect was maintained throughout the experiment to completely digested lignocellulosic substrate.ConclusionsThe induced enzyme solution collected from a microbial methanogenic community contained enzymes that were apparently active and stable in the environment of anaerobic digestion. The enzymatic activity had a profound effect on the biogas production rate and yield, comparable with the results of many pretreatment methods. Thus, application of such enzymes could enable efficient low energy in situ anaerobic digester treatment for increased biomethane production from lignocellulosic material.

Metaproteomics-guided selection of targeted enzymes for bioprospecting of mixed microbial communities

“…10 ml of cooled extraction buffer (2× [50 mM Tris–HCl, pH 8,5, 5 mM EDTA, 100 mM KCl, 1% (w/v) DTT, 30% (w/v) sucrose]), containing the cOmplete protease inhibitor mix (Roche) were added to the 10-ml concentrated sample [24]. After vortexing, protein samples were extracted with 10 ml Tris-buffered phenol, pH 8.0 (Sigma, Germany).…”

Granular Sludge Bed Processes in Anaerobic Digestion of Particle-Rich Substrates

“…Several studies have shown promising results with regard to increased hydrolysis as well as increased biogas production due to the addition of enzymes [87]. Enhancing the degradation of lignocellulosic substances using enzymes that degrade lignin, cellulose, and other polysaccharides has been the focus of enzymatic treatment studies.…”

“…dX C dt = −K h S surf (8) where S surf is the surface area of solid particulates and ρ solid is the density of solid particulates. Various authors report that Contois kinetics provides a better fit for AD of complex substrates compared to first-order kinetics [86][87][88]. Contois kinetics (Equation (9)) takes effects of active biomass (X biom ) and its ratio to the slowly degradable substances (Xc) in the substrate into account.…”

Comparison of pretreatment methods that enhance biomethane production from crop residues - a systematic review

“…show that combined processes are high energy-consuming methods(Gumisiriza et al, 2017;Speda et al, 2017;Perendeci et al, 2018). High temperatures and limited heat recovery during steam explosion (SE) pretreatment may lead to high energy use and reduced methane yield(Gumisiriza et al, 2017).…”