Characterization of Soyhull Fiber Digestion by In Situ and In Vitro Enzymatic Procedures

Abstract

Soyhulls (original form), neutral detergent and acid detergent fiber extracted from soyhulls were characterized by rates of dry matter disappearance by in situ and in vitro enzyme procedures. Enzyme combinations were cellulase, pectinase, cellulase – hemicellulase, cellulase – pectinase, and cellulase – hemicellulase – pectinase. Incubation times for both in situ and in vitro procedures were 0, 1, 2, 6, 8, 12, and 24h. Two additional independent time sequences of soyhulls used in situ and cellulase procedures for extended times of 36, 48h and 36, 48, 60, and 72h.In situ rates of dry matter disappearance were similar to in vitro enzyme systems with cellulase or cellulase – hemicellulase for original hulls at 24h. In situ neutral detergent fiber disappearance was similar to cellulase, and acid detergent in situ disappearance similar to cellulase – pectinase. Addition of pectinase to cellulase or cellulase – hemicellulase increased dry matter disappearance for original and neutral detergent hulls but not acid detergent hulls. In situ rates of dry matter disappearance for original soyhulls increased with incubation time at 72h compared to 24 and 48h, emphasizing the importance of extended incubation for this technique. In vitro rates for cellulase decreased with incubation beyond 24h, suggesting caution in interpretation of rate for in vitro enzymatic systems using extended intervals.