Growth-enhancing substrates

Another generalization of the Monod-type kinetics was suggested by Tsao and Hanson (1975) and by Tsao and Yang (1976). They assumed the existence of growth-enhancing substrates Si and of essential substrates resulting in an equation... 

The effect of growth-enhancing substrates is given as the sum of Monod-type... 

The proposal made by Megee et al. (1972) is valid whenever limiting substrates are consumed simultaneously and both are essential for growth. This means that growth is interrupted when complete consumption of any substrate occurs, even though the other substrate is in excess. Dunn et al. (1992) proposed the idea of enhancing substrates that are non-essential, but if available they can improve specific cell growth rate (Equation 20). 

D. Rotin, A. M. Honegger, B. L. Maigolis, A. Ullrich, and J. Schlessinger. Presence of SH2 domains of phospholipase C gamma 1 enhances substrate phosphor tion by increasing the affinity toward the epidermal growth factor receptor. J Bid Chem, 267 (14), 9678-9683, 1992. 

Particle size is one of the important parameters that help the gaseous exchange as well as heat and mass transfer between particles. It affects the surface area-to-volume ratio of the particle that is initially accessible to the microorganism and the packing density within the surface mass. The size of the substrate determines the void space, which is occupied by air. Since the rate of oxygen transfer into the void space affects growth, the substrate should contain particles of suitable size to enhance mass transfer. 

Yin PM, Nishina N, Kosakai Y, Yahiro K, Park Y, Okabe M (1997) Enhanced production of (L)-LA from com starch in a culture Rhizopus oryzae using an air-Uft bioreactor. J Ferment Bioeng 84 249-253. doi 10.1016/S0922-338X(97)82063-6 Zacharof MP, Lovitt RW (2013) Modelling and simulation of cell growth dynamics, substrate... 

The rate of side-chain cleavage of sterols is limited by the low solubiUty of substrates and products and thek low transport rates to and from cells. Cyclodextrins have been used to increase the solubiUties of these compounds and to assist in thek cellular transport. Cyclodextrins increase the rate and selectivity of side-chain cleavage of both cholesterol and P-sitosterol with no effect on cell growth. Optimal conditions have resulted in enhancement of molar yields of androsta-l,4-diene-3,17-dione (92) from 35—40% to >80% in the presence of cyclodextrins (120,145,146,155). 

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