Biomass growth limitations

Biomass feedback refers to increasing the concentration of biomass in the culture vessel. This is achieved by fitting some device, either internally or externally, to the continuous culture which retains or returns biomass to the vessel. The main advantage of biomass feedback is that the maximum output rate of biomass (and products) in the vessel with a given medium can be increased. This is particularly useful when the growth-limiting substrate is unavoidably dilute, for example if substrate has low solubility or has to be limited because of the formation of an inhibitory product. 

Aim3 aerobic bioprocess was operated in a continuous mode with nitrogen as the growth limiting nutrient. The steady state biomass concentration (x), the biomass yield coefficient (Yx/S) and the product yield coefficient (Yp/t) were determined at a low and at a high dilution rate (D). 

Turner, R. E., N. N. Rabelais, and Z. N. Zhang. 1990. Phytoplankton biomass, production and growth limitations on the Huanghe (Yellow River) continental shelf. Continental Shelf Research 10 545-571. 

Mineralization of organic residues in soil is mainly carried out by an extremely diverse heterotrophic community referred to as the soil microbial biomass. The soil environment is a rather peculiar natural environment for the growth of microorganisms, in that they have had to adapt to quite extreme growth-limiting factors (a) discontinuous availability of substrates and water and (b) high variability of soil chemical properties (pH, temperature, oxygen supply) that can vary in the soil environment on both the micro and macro scales (Jenkinson and Ladd, 1981). 

First, solve for rsu using the information given in the table and the following equation, in which X is biomass concentration, S is growth-limiting substrate concentration, and Ks is the substrate concentration at one-half the maximum specific substrate-utilization rate ... 

Monod-Type Empirical Kinetics Many bioreactions show increased biomass growth rate with increasing substrate concentration at low substrate concentration for the limiting substrate, but no effect of substrate concentration at high concentrations. This behavior can be represented by the Monod equation (7-92). Additional variations on the Monod equation are briefly illustrated below. For two essential substrates the Monod equation can be modified as... 

Another biomass approach is ocean fertilization. This method spurs biomass growth in areas that are low in productivity due to lack of critical nutrients. It, too, is limited in capacity, and has raised environmental concerns over changes in the natural food chain. The cost of biomass conversion is often quite low. Faustian et al.F l estimate that planting forests in developing countries could cost as low as US 3-10 per ton of CO2 captured. 

Fig. 1 Example of processing stages used to evaluate the images of biomass growth from solid-state fermentation (experimental condition 24 h of fermentation) a acquired image b a high-pass filter is applied c a limited threshold is applied, and d debris are removed to reach the final image...

To compare the performance of the three yeast species and to prevent growth limitations due to any nutritional deficiency, the BSG hydrolyzate was supplemented with several mineral nutrients and vitamins to reach the concentrations described in Duarte et al. [17], D. hansenii biomass production for subsequent studies was carried out using a previously optimized medium containing 0.5 g F KH2PO4 as the only supplement to BSG hydrolyzate [2]. To prevent nutrient thermal decomposition, all media were filter sterilized using a 0.22-pm Gelman membrane filters (Pall Corporation, Arm Arbor, MI, USA). 

As the primary trophic levels increase in biomass, growth in the small microflagellate and heterotrophic bacterial communities increase in kind. It appears that these consumers of recently fixed carbon (both particulate and dissolved) respond to the food source and not necessarily the iron (although some have been found to be iron-limited). Because their division rates are fast, heterotrophic bacteria, ciliates, and flagellates can rapidly divide and... 

Material balances on the substrate and the product species can be used with a rate expression and yield coefficients to specify completely the compositions of the remaining streams in Figure 13.8. For a generic biomass specific rate law and steady-state operation, a balance on the growth-limiting substrate around the combination of the mixing point and the bioreactor indicates that... 

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