| Rhizopus oligosporus sporangiospores are used as starters for the production of tempeh, a fermented soyfood. The increasing popularity of this product in the United States prompted the present investigation to study the production, preservation, and germination of R. oligosporus sporangiospores. The possibility of a semi-continuous fermentation for the manufacture of tempeh was also suggested.;A method for preservation of R. oligosporus sporangiospores on activated silica gel was described. Under optimal conditions of storage (4 C, 30% R.H.), sporangiospores survived for at least one year without any substantial loss in viability.;Germination of sporangiospores involved two consecutive phases: Phase I (swelling) and Phase II (germ tube protrusion). Optimal pH and temperature for germination were pH 4.0 and 42 C. Sporangiospores contained insufficient carbon reserves for swelling or germination to occur in distilled water. Initial swelling (Phase I) required the presence of exogenous carbon. Subsequent production of germ tubes (Phase II) required both exogenous carbon and nitrogen. Inhibitor studies suggested that swelling and germination require active protein synthesis and respiratory energy. Spores germinated most rapidly in mixtures of amino acids, with L-proline and L-alanine most effective. D-glucose, D-xylose, and D-mannose were the most effective carbon sources for germination.;A heat-stable, dialysable factor(s) present in an aqueous soybean extract (soybean cook water) promoted more rapid and more efficient germination than was noted on other media. The factor(s) also resulted in increased diameter during Phase I and multiple germ tubes in Phase II. Results suggested soybean cook water may provide a useful medium for studies of spore germination and spore injury.;A defined medium was used to identify nutritional aspects of sporangiospore production and longevity. Sporangiospore production was favored by a 23:1 C/N ratio and 0.05 M Na(,2)HPO(,4) in the medium. The presence of 0.05 M Na(,2)HPO(,4) in the spore production medium also enhanced survival of sporangiospores during initial storage.;Several novel approaches for the production of tempeh were examined, including a two-stage incubation, and use of a germinated inoculum. Satisfactory tempeh could not be produced using an initial incubation (4-8 h) at 42 C prior to transfer to 30 C; however, satisfactory tempeh was produced using a germinated inoculum. Fermentation time was decreased by 25 to 30 percent. This savings in time would result in improved economics for tempeh manufacture. |
