Development of a Serial Bioreactor System for Direct Ethanol Production from Starch Using Aspergillus niger and Saccharomyces cerevisiae

다국어 초록 (Multilingual Abstract)

Aspergillus niger hyphae were found to grow with unliquefied potato starch under aerobic conditions, but did not grow under anaerobic conditions. The raw culture of A. niger catalyzed saccharification of potato starch to glucose, producing approximately 12 g glucose/L/day. The extracellular enzyme activity was decreased in proportion to incubation time, and approximately 64% of initial activity was maintained after 3 days. At $50^{\circ}C$, A. niger hyphae growth stopped, while the extracellular enzyme activity peaked. On the basis of the A. niger growth property and enzyme activity, we designed a serial bioreactor system composed of four different reactors. Fungal hyphae were cultivated in reactor I at $30^{\circ}C$, unliquefied starch was saccharified to glucose by a fungal hyphae culture in reactors II and III at $50^{\circ}C$, and glucose was fermented to ethanol by Saccharomyces cerevisiae in reactor IV. The total glucose produced by fungal hyphae in reactor I and saccharification in reactor II was about 42 g/L/day. Ethanol production in reactor IV was approximately 22 g/L/day, which corresponds to about 79% of the theoretical maximum produced from 55 g starch/L/day.