Enzymatic Conversion of Corn Cobs to Glucose with Trichoderma Viride Fungus and the Effect on Nutritional Value of the Corn Cobs

Abstract

Three experiments were conducted with a cellulase-producing fungus, Trichoderma viride, on corn cobs. A microbial plating technique was used to determine the capacity of Trichoderma viride to exert cellulase activity on various levels of noble agar (1 and 2%) and corn cob substrate concentrations (2, 3,4 and 5%). A significant decrease in cellulase activity was observed when noble agar was increased from 1 to 2%. Varied corn cob substrate concentrations had no effect on degree of clearing around wells (P<.05), indicating that cellulase permeability is not affected by corn cob concentrations at the levels used in this study. A randomized factorial design measured the capacity of Trichoderma viride to degrade corn cobs as indicated by glucose production in in vitro fermentation. The five factors studied were: (1) two temperatures, 23 and 37 C; (2) two particle sizes of corn cobs, coarse ground through a 12-mm screen (as feed milled) and fine ground through a 1-mm screen; (3) two ratios of corn cobs to water (1:4 and 1:6 by weight); (4) nine intervals (1 to 9 weeks); and (5) inoculation of cobs with Trichoderma viride vs no inoculation. Glucose production was maximized (P<.01) in wk 4 with a combination of finely ground corn cobs inoculated with Trichoderma viride, a temperature of 23 C and a 1:6 ratio of corn cobs to water. One rat growth trial and one sheep digestibility trial were conducted to investigate nutritional effects of feeding corn cobs treated with the cellulase-producing fungus, Trichoderma viride. In the rat growth trial, untreated or treated ground corn cobs replaced 0, 60, 80 or 100% of the glucose of the control diet. At each of the substitution rates, use of treated corn cobs improved (P<.05) gain over that obtained when untreated corn cobs were used. In the lamb digestion trial, treated and untreated cobs were compared in a diet containing 40% ground corn cobs. Use of treated corn cobs resulted in increases (P<.01) in digestibility of dry matter (4.8%), N-free extract (9%) and total digestible nutrients (18%), decreases (P<.01) in digestibility of crude fiber (41%) and ether extract (8.8%), and no significant change in digestibility of crude protein.