Production of hydrolytic enzymes by the plant pathogenic fungus Myrothecium verrucaria in submerged cultures

A capacidade do fungo fitopatogênico Myrothecium verrucaria produzir enzimas hidrolíticas extracelulares em culturas submersas foi estudada utilizando diversos substratos. O fungo foi capaz de produzir diferentes depolimerases e glicosidases, sendo xilanases, pectinases e proteases as mais importantes. Atividade lipase foi encontrada nos filtrados das culturas desenvolvidas na presença de óleo de oliva, enquanto atividade proteolítica foi detectada em todas as culturas. Xilanase e pectinase foram otimamente ativas em pH 4,5 a 5,5, enquanto protease foi ativa em ampla faixa de pH (3,5 a 11,0). As três enzimas foram otimamente ativas 40ºC e estáveis por várias horas a temperaturas até 50ºC.

A thermostable maltose-tolerant alpha-amylase from Aspergillus tamarii.

An homogeneous fraction of alpha-amylase from Aspergillus tamarii was obtained by means of a very easy purification procedure. The enzyme is a glycoprotein containing 32% saccharide and MW of 37.5 kDa. Optimal of pH and temperature with starch as substrate were 4.5-6.5 and 50-55 degrees C. The enzyme was stable for several hours at temperature up to 65 degrees C. Starch, amylose, and amylopectin were the substrates preferentially hydrolysed and maltose and maltotriose were the main end products. The values of K(M) and V(max) for starch were 2 g/l and 880 micromoles reducing sugars/min.mg of protein, respectively. The purified enzyme was remarkably insensitive to end product inhibition, being only slightly inhibited by maltose and glucose up to 1.0 M.

Temperature effect in the production of multiple xylanases by Aspergillus fumigatus.

This work has evaluated the temperature effect in the production of multiple xylanases by a locally isolated strain of Aspergillus fumigatus Fresenius. Three isoenzymes, identified as xylanases I, II, and III with apparent molecular weight of 45.7 KDa, 39.8 KDa and 18.2 KDa, respectively, were produced in cultures developed at 30 degrees C and at 42 degrees C. The pattern of distribution of xylanase activity among the three isoenzymes was greatly affected by the growth temperature: at 30 degrees C, the total xylanase activity was distributed homogeneously among the three enzymes, while at 42 degrees C, the total xylanase activity was mainly due to the fractions with the highest MW (I and II) and the xylanase III was a minor component.

Production of amylases by Aspergillus tamarii

A strain of Aspergillus tamarii, a filamentous fungus isolated from soil, was able to produce both Ó-amylase and glucoamylase activities in mineral media supplemented with 1(per cent) (w/v) starch or maltose as the carbon source. Static cultivation led to significantly higher yields than those obtained using shaking culture. The production of amylases was tolerant to a wide range of initial culture pH values (from 4 to 10) and temperature (from 25 to 42degree C). Two amylases, once Ó-amylase and one glucoamylase, were separated by ion exchange chromatography. Both partially purified enzymes had optimal activities at pH values between 4.5 and 6.0 and were stable under acid conditions (pH 4.0-7.0). The enzymes exhibited optimal activities at temperatures between 50(degree) and 60(degree) C and wete stable for more than ten hours at 55(degree) C.