Bioprocess strategies for mass multiplication of and metabolite synthesis by plant growth promoting pseudomonads for agronomical applications

Abstract

The exponential substrate feeding (open-loop) and automated feedback substrate feeding (closed loop) strategies were developed to obtain high cell densities of fluorescent pseudomonad strains R62 and R81 and enhanced production of antifungal compound 2,4-diacetylphloroglucinol (DAPG) from glycerol as a sole carbon source. The exponential feeding strategy resulted in increased glycerol accumulation during the fed-batch cultivation when the predetermined specific growth rate (μ) was set at 0.10 or 0.20h−1 (<μm=0.29h−1). Automated feeding strategies using dissolved oxygen (DO) or pH as feedback signals resulted in minimal to zero accumulation of glycerol for both the strains. In case of DO-based feeding strategy, biomass productivity of 0.24g/(Lh) and 0.29g/(Lh) was obtained for R62 and R81, respectively. Using pH-based feeding strategy, biomass productivity could be increased to a maximum of 0.51 and 0.54g/(Lh), for the strains R62 and R81, respectively, whereas the DAPG concentration was enhanced to 298mg/L for R62 and 342mg/L for R81 strains. These yields of DAPG are thus far the highest reported from GRAS organisms.