RESUMEN
The production of arabinoxylan-degrading enzymes by the fungus Penicillium brasilianum, grown on different carbon and nitrogen sources as well as different environmental conditions was investigated. Highest feruloyl esterase (225 mU/ml) and alpha-L-arabinofuranosidase (211 mU/ml) activities were obtained when P. brasilianum was grown on sugar beet pulp, whereas maximum xylanase (17 U/ml) activity was found during growth on oat spelt xylan. Yeast extract was the preferable nitrogen source for the production of all the three enzymes. Further optimization of the production of the crude enzyme mixture was examined by experimental design using a D-optimal quadratic model. Investigation of the microbial regulation of enzyme production showed that the presence of free ferulic acid further stimulated the production and pointing to that the fungal regulatory mechanism involved a coordinated production and secretion of feruloyl esterase, xylanase and alpha-L-arabinofuranosidase. Since agroindustrial by-products are a potential source of phenolic acids, crude enzyme mixtures of P. brasilianum were tested for their hydrolysis abilities against eight complex or model substrates. While total release of phenolic acids and pentoses was not observed, the synergistic enhancement of hydrolysis in the presence of feruloyl esterase was clearly demonstrated.
Asunto(s)
Hidrolasas de Éster Carboxílico/metabolismo , Pared Celular/metabolismo , Penicillium/enzimología , Plantas/metabolismo , Análisis de Varianza , Carbono/metabolismo , Pared Celular/efectos de los fármacos , Ácidos Cumáricos/metabolismo , Ácidos Cumáricos/farmacología , Inducción Enzimática , Concentración de Iones de Hidrógeno , Hidrólisis/efectos de los fármacos , Nitrógeno/metabolismo , Pentosas/metabolismo , Plantas/efectos de los fármacos , Temperatura , Factores de TiempoRESUMEN
The production of a battery of arabinoxylan-degrading enzymes by the fungus Penicillium brasilianum grown on brewer's spent grain (BSG) under solid-state fermentation was investigated. Initial moisture content, initial pH, temperature, and nitrogen source content were optimized to achieve maximum production of feruloyl esterase, xylanase, and alpha-L: -arabinofuranosidase. Under the optimum growth conditions (80% moisture, pH 6, 26.5 degrees C, and 5 g/l nitrogen source), the maximum level of feruloyl esterase (1,542 mU/g BSG) was found after 196 h, whereas xylanase (709 U/g BSG) and ArabF activity (3,567 mU/g BSG) were maximal after 108 h and 96 h, respectively. Based on substrate utilization data, the feruloyl esterases produced by P. brasilianum was anticipated to subclass B. A crude enzyme (CE) preparation from P. brasilianum culture grown on BSG was tested for the release of hydroxycinnamic acids and pentoses from BSG. The P. brasilianum CE produced in this work contains a balance of cell wall-modifying enzymes capable of degrading arabinoxylan of BSG by more than 40%.