Kanchanasuta S., Haosagul S., Pisutpaisal N., 2016, Metabolic Flux Analysis of Hydrogen Production from Rice Starch by Anaerobic Sludge under Varying Organic Loading, Chemical Engineering Transactions, 49, 409-414.
Metabolic flux analysis (MFA) was used to evaluate the impact of organic loading of rice starch fermentation by an anaerobic sludge on the H2 production. H2 production was conducted in 0.5 L batch reactor under varying organic loading in the range of 2.5 to 12.5 g/L, initial pH of 6 and 37oC. Maximum H2 production, the percentage of starch hydrolysis and glucose utilization were observed at 5 g/L starch. Acetate was the main carbon fraction after 20 h fermentation for all cases. Acetate production, an objective function, was maximized with respect to H2 production pathway. Results indicated that acetate production pathway was correlated not only to the H2 production but it also the H2 consumption through acetogenesis (R17). Intracellular butyrate oxidation (R26) was strongly correlated to the acetate production and H2 production. The organic loading strongly impact the principal flux of H2 production. Re-oxidizing ferredoxin pathway (R13) plays a significant role on the maximum H2 flux only at low organic loading (= 5 g/L starch). However, H2 flux obtained from butyrate oxidation reaction (R26) and re-oxidizing ferredoxin pathway (R13) was not significantly different at high organic loading (7.5 to12.5 g/L). Butyrate oxidation could be used as a strategic reaction target to promote the performance of the involved microorganisms in the reactor to achieve the high H2 production. MFA calculated from the in silico model was a crucial information for enhancing the H2 production by the mixed culture.
