Bottlenecks of anaerobic degradation of proteins in sewage sludge and the potential targeted enhancing strategies

Proteins degradation plays a decisive role in the biogas production and subsequent dehydration of sewage sludge. And the anaerobic degradation of proteins in sewage sludge is limited by enzymatic hydrolysis barrier during hydrolysis process, selectivity and underutilization during amino acids fermentation, as well as molecular toxicity effects of metabolic products. Traditional pretreatments could solely improve the hydrolysis and even brought inhibition on the latter metabolism processes. In order to overcome the above bottlenecks, regulating microorganisms, secretion and activity of key enzymes, as well as interspecies electron transfer are proposed to be potential strategies of targeted enhancement of proteins degradation in sewage sludge. Since complex organic matters restricted the domestication of microorganisms and key enzymes that targeted degrade refractory proteins in sewage sludge, more profound investigations on regulating methods based on ORP control, bio-stimulation and AD-MEC etc. are needed to screen and domesticate the targeting microorganisms and enzymes related to refractory proteins degradation in AD systems. Moreover, more research should also be focused on the components and physical-chemical characteristics of refractory proteins in sludge and also their isolation strategies, especially which are remained in anaerobic digestate of sewage sludge after traditional pretreatments. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Proteins degradation is crucial in biogas production and sewage sludge dehydration, but faces barriers like enzymatic hydrolysis, fermentation selectivity, and toxic effects of metabolic products. To enhance degradation, regulating microorganisms, key enzymes, and interspecies electron transfer are proposed strategies. More research is needed to domesticate targeting microorganisms and enzymes for degrading refractory proteins in sewage sludge.