Batch and Repeated-Batch Fermentation for 1,3-Dihydroxyacetone Production from Waste Glycerol Using Free, Immobilized and Resting Gluconobacter oxydans Cells

Conversion of biodiesel derived waste/crude glycerol to higher value products is a potential way for enhancing the economy of biodiesel industry. Among several products, dihydroxyacetone (DHA) is one of the fine chemicals known to be used in pharmaceutical and cosmetic industry. However, microbial DHA production by Gluconobacter oxydans is inhibited by high concentration of substrate as well as product. Therefore, the present study is focused on DHA production by batch and repeated-batch fermentation to obviate the substrate inhibition effect. Apart from using free cells for fermentation experiments, this study is more focused towards use of immobilized and resting G. oxydans cells with pure/crude glycerol as substrate. For batch experiment with immobilized cells, a final DHA concentration of 17.83g/L was observed in presence of pure glycerol, which was approx. ninefold higher than free and resting cells experiments. Repeated-batch experiment with four times crude glycerol feeding (10g/L each time) resulted a DHA concentration of 35.95g/L, with 89.88% conversion rate within 96h of fermentation. Increase in initial glycerol feed and final DHA concentration in the fermentation broth, decreased the value of rate constant (k(1)), which further corroborate the substrate and product inhibition effect. [GRAPHICS] .