7 January 2020 - A new model to calculate the microbial allocation of enzymes

7 January 2020 - A new model to calculate the microbial allocation of enzymes produced over soil decomposition

Plant litter is composed of different chemical compounds, such as cellulose, hemicelluloses and lignin whose decomposition is catalyzed by extra-cellular enzymes produced by soil microorganisms. However, the mechanisms of decomposition are complicated by the physical and chemical links between cellulose, hemicelluloses and lignin that require different enzymes to cleave.

Hydrolytic enzymes depolymerize cellulose whereas oxidative enzymes depolymerize lignin. Cellulose and hemicelluloses are energy rich polysaccharides whereas lignin is a polyphenolic compound and likely energy sink for catalysis. However, biochemical linkages between polysaccharides and lignin may also necessitate the breakdown of lignin to increase access to cellulose and hemicelluloses. The lignocellulose index (LCI = lignin/ [lignin + cellulose + hemicelluloses] of plant litter has long been used a strong predictor of decomposition rate. We developed a model to calculate the allocation of hydrolytic and oxidative enzymes to match observed decays rates of cellulose + hemicelluloses and lignin, respectively, given litter lignocellulose index. Results were consistent with empirical long-term experimental studies that couple measurements of litter chemistry and microbial enzyme activities. Our study raises further questions about factors controlling the LCI threshold values at which oxidative enzymes are produced because it varies among studies, such as with nitrogen availability.

Article: Margida, M.G., Lashermes, G., Moorhead, D.L. (2020) Estimating relative cellulolytic and ligninolytic enzyme activities as functions of lignin and cellulose content in decomposing plant litter. Soil Biology and Biochemistry 141, 107689. DOI

Contact: Dr Gwenaëlle Lashermes, gwenaelle.lashermes@inra.fr

Pr Daryl Moorhead, daryl.moorhead@utoledo.edu

Modification date: 06 June 2023 | Publication date: 07 January 2020 | By: G. Lashermes