Production of 1,3-Dihydroxyacetone by Gluconobacter nephelii in Upflow Aerated Bioreactors with Agro-industrial Wastes as External Nitrogen Source

Cultivation of recently identified Gluconobacter nephelii to produce 1,3-dihydroxyacetone (DHA) was conducted using the growth medium containing the external nitrogen source from agro-industrial wastes. Cell cultivation in 250 mL glass flasks using 80 g/L glycerol and corn steep liquor as nitrogen source yielded the highest biomass (1.75 ± 0.23 g/L) and DHA (49.5 ± 3.14 g/L) concentrations as compared to other nitrogen sources (i.e., glutamic mother liquor and soybean meal hydrolysate). Subsequent cultivation in larger bioreactors (32 L) with corn steep liquor as the preferred nitrogen source indicated that internal-loop airlift bioreactor yielded significantly higher biomass and DHA concentrations than flat-panel airlift and bubble column bioreactors. Further optimization of internal-loop airlift photobioreactor revealed that DHA production in G. nephelii depended on the aeration rates, with the maximum DHA concentrations (46.09 ± 1.01 g/L) obtained when maintaining the aeration rates at 0.64 vvm.