| A hyperproducing α-galactosidase (GAL) strain was screened from Penicillium janczewskii through physical and chemical compound mutagenesis. The conditions of solid-state fermentation (SSF), including cultivating environmental factors and culture compositions, were optimized, and the pilot-scale production of GAL in SSF was performed. Moreover, the properties and applications in broiler on the enzyme preparation were studied. Firstly, the assay of feed Penicillium GAL activity was established as the para-nitrophenol spectrophotometeric method. It was suitable to specify GAL determination under the conditions of pH 5.5, 40℃, 10 min reaction at 405 nm. The original strain was treated repeatedly with ultraviolet light, ethyl methane sulfonate, and nitrosoguanidine in turn, and five strains with hyperproducing GAL were selected. With sequential generation, then circulatory and alternative culture, Penicillium sp. MAFIC-6 was obtained since it is stable and high production. Its basic GAL activity is about 147 U/g. GAL synthesis from MAFIC-6 is repressed by glucose to a certain extent, whereas induced by sucrose, melibiose and raffinose, which suggested the strain is a partially constitutive. Various factors effecting enzyme production were studied in Erlenmeyer's flasks and trays. The results showed that the best GAL activity could be available with 50.7 g substrate on the initial pH 5.5-6.5 and 55% moisture content, incubating at 26~32℃ for 75 h. Tests on SSF in trays disclosed the changes of temperature and water in the course of fermenting process. When the inner temperature of the culture rises, the water content of culture drops. Apple pulp, beet pulp, and bagasse can partially substitute wheat bran as carbon sources for GAL production. Yeast meal and soybean meal are better nitrogen sources than others. Adding 0.1% Tween-80, Triton-100, or EDTA to the culture markedly improved GAL activity. An orthogonal design was employed to optimize the composition of the culture. GAL activity reached the highest (172 U/g) when the levels of soybean meal, beet pulp, (NH4)2SO4, and K2HPO4 were 16%, 4%, 2% and 2% respectively in the medium. The following response surface methodology indicated that the recipe of soybean meal at 19.20%, beet pulp at 3.89%, and K2HPO4 at 2.92% amounted to the theoretical value 174.98 U/g, coinciding with the practical result. In natural SSF the temperature and water of culture varied greatly and the final activity was 128.5 U/g. However, under controlled condition the temperature and water changed little and the final activity was 166.3 U/g that increased 29.4% compared with the natural. Ventilation and spraying sterile water may be effective measures to mediate temperature and water balance. The crude GAL is optimal at pH 3.5~6.5 and 50~60℃. Metal ions affected GAL activity. The Km and Vm of GAL to para-nitrophenyl-a-D-galactopyranoside is 1.38 mmol L-1 and 2.58 mmol L-1 s-1. Finally, the effects of GAL supplementation of corn-soybean meal diet on nutrient utilization, performance, serum indices and organ weight in broilers were studied. The results indicated that adding GAL enhanced metabolizable energy and nutrient digestibility to the diets, and obviously improved performance of broilers in the early growth stage. The interaction of GAL and energy can be also detected by some parameters determined.
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