Vitamin B12 production in tempeh by non-sequential mixed fermentation at laboratory and bench scales.

Results of the study showed that Lactobacillus casei did not affect the vitamin B12 production of P. shermanii 1250 in tempeh when added during the soaking of the beans and also when added with Propionibacterium shermanii 1250 during fermentation. The optimum conditions obtained for vitamin B12 production by P. shermanii 1250 in tempeh at laboratory scale consisted of 55% moisture content of the beans (50 g in Petri dish), mixed culture of 5.0% P. shermanii 1250 and 0.5% Rhizopus oligosporus inoculum and incubation temperature of 35 deg C for 24-48 hr. The highest yield of vitamin B12 obtained at optimum conditions was 308.4 mg per 100g. In general, compounds such as protein, fat, ash, and amino nitrogen increased during fermentation while carbohydrate (by difference), soluble carbohydrate and fiber decreased as fermentation time progressed. In addition, the concentration of most of the amino acids, especially lysine and methionine, were higher in high vitamin B12-tempeh as compared with those in the unfermented soybean. Optimum conditions used in bench scale were similar to that used in laboratory scale. Bench scale production of high vitamin B12-tempeh, performed in stainless steel trays (30 cm x 45 cm x 3 cm), yielded 297.47 mg vitamin B12 per 100 g of mixture at optimum conditions of 2 cm thickness of sterilized soybean mass (1,400 g per tray) covered with non-perforated aluminum foil, and incubation period of 24 hr at 35 deg C. The chemical composition of high vitamin B12-tempeh produced in trays at optimum conditions was also similar to that produced in laboratory scale. The mass balance in the production of high vitamin B12-tempeh in the tray at optimum conditions showed 30.14% of total solids was lost during processing. Some intermediate metabolites involved in the pathway of vitamin B12 by P. shermanii 1250 in tempeh (as detected by gas chromatography) included acetic acid which increased and propionic acid which decreased as fermentation time progressed. Moreover, succinic acid and glycine decreased during fermentation.