A mathematical approach for the estimation of biomass production rate in solid state fermentation

Abstract

The oxygen uptake rate (OUR) was studied in a solid state fermentation process of dried citrus peel with the strain Asporgillus niger QH-2 in order to obtain the growth estimation of the microorganism in the system. The relationship between OUR, the maintenance coefficient (m) and the yield for oxygen consumption (Yo,) allows the estimation of the biomass rate if we consider that both parameters are not constants in some periods of the process. It was estimated t h a t in the first 24h the strain has a n specific growth rate of 0.174 h-1 with values for Yo, and m in the order of 2.84 g-cell/g-oxygen and 0.006 g-osygen/g-cell -h respectively.

Solid-state fermentation : modelling fungal growth and activity

“…During this lag phase, dXtlf is zero and Xis equal to X 0 , the initial amount of viable biomass. Since a large problem in SSF is the quantitative separation of biomass from its substrate, usually concentrations of biomass-related constituents are measured and used, such as the amounts of glucosamine (8,11,12), protein (13,14,15), ATP (16, 17), C0 2 (9) and 0 2 (5,18). Alternatively, the pressure drop over a packed bed has been correlated to biomass growing on an inert carrier (19) and used in modelling as well (20).…”

“…The reaction was stopped by adding dinitrosalysilic acid solution (DNS) and further treated according to the method described by Wood and Bhat (13). Activities were calculated against glucose standard and corrected for activities found in blanks without substrate and blanks without enzyme.…”

“…From the suspension 1.8 ml was taken which was pre-heated at 50 °C and incubated for exactly 10 min with 0.2 ml of the diluted extract. The reaction was stopped by adding DNS, and xylanase activity was calculated according to the method described by Wood and Bhat (13). Xylose was used as standard .…”

“…This will continue until another parameter becomes restrictive. Oxygen exhaustion has been measured in a small fermenter chamber (13). This was also predicted to occur in an isothermal system (21).…”

“…Due to elevated temperature, lack of oxygen or high carbon-dioxide concentrations, inhibition of microbial growth and activity can occur. Temperature increase, low oxygen and high carbon dioxide concentration occur faster in the core of the fermenter bed than in the outer layers, and thus inhibition effects differ among locations in the bed (13). This results in inhomogeneity of the substrate layer.…”