Seminar in Applied Mathematics

Nicolai Panikov Institute of Microbiology Russian Academy of Sciences and Department of Chemistry & Chemical Biology Stevens Institute of Technology Mathematical simulation of microbial decomposition: From fictional chemistry to the natural biological reality Tuesday, February 22, 2000 3:00pm Pierce 116

Abstract:   Decomposition of organic matter is a globally important biospheric process, which closes up the C cycle. In industry and agriculture, the understanding of decomposition is needed to optimize a number of modern and classic biotechnologies (waste management, biogas production, composting, crop rotation). My main intent is to show how mathematical simulation can clarify the underlying mechanisms and help to develop an efficient process control. Most of known mathematical models of decomposition are dominated by simplistic and formal approach borrowed from chemical kinetics, e.g. self-decay of heterogeneous detritus, ds/dt = -Sum(k_i*s_i) where s_i represents one of n individual components, t is time, and k_i are respective first-order rate constants. Some models instead of s_i contain the distribution f(z,t) of decaying compounds with respect to imaginary parameter z, the susceptibility to microbial degradation and account for simultaneous decay and transformation V(z,t) of original detritus to other chemical species, f_t + V_t = -U*f where U(z,t) is the vector of degradation rates. Instead of imaginary self-decay and transformation reactions, we introduced more accurate models based on the real operating mechanisms. They include microbial consumption and oxidation of consumed substances, induction and repression of hydrolytic enzymes, competition between microbial populations, limitation and inhibition of microbial growth, effect of environmental conditions, etc. I will show the particular ways to avoid an excessive complexity of such simulations keeping the models manageable (sets of 3-10 ordinary differential equations). The developed simulations allowed us to identify the main reasons of slow decomposition of some particular plant litter (combine effect of metabolic inhibition and limitation by inorganic nutrients) and explain some intriguing phenomena associated with litter decomposition (priming action and unexpected interruption of decay, effects of drying-rewetting, freezing-thawing, etc.)

Coffee and refreshments will be available starting at 3:00pm. For additional information contact Patrick Miller  or Yi Li.