Eduardo da Silva Martins

Pectinase production by Penicillium viridicatum RFC3 by solid state fermentation using agricultural wastes and agro-industrial by-products

Pectin lyase and polygalacturonase production by newly isolated Penicillium viridicatum strain Rfc3 was carried out by means of solid state fermentation using orange bagasse, corn tegument, wheat bran and mango and banana peels as carbon sources. The maximal activity value of polygalacturonase (Pg) (30U.g -1 ) was obtained using wheat bran as carbon source while maximal pectin lyase (Pl) (2000 U.g -1 ) activity value was obtained in medium composed of orange bagasse. Mixtures of banana or mango peels with sugar cane bagasse resulted in increased Pg and Pl production compared to fermentations in which this residue was not used. The mixture of orange bagasse and wheat bran (50%) increased the production of Pg and Pl to 55 U.g -1 and 3540 U.g –1 respectively. Fractions of Pg and Pl, isolated by gel filtration in Sephadex G50, presented optimum activity at pH 5.0 and 10.5 respectively. Maximal activity of Pg and Pl fractions was determined at 55oC and 50oC respectively. Pg was stable in neutral pH range and at 40oC whereas Pl was stable in acidic pH and at 35oC, for 1 h.

Purification and Properties of Polygalacturonase Produced by Thermophilic Fungus Thermoascus aurantiacus CBMAI-756 on Solid-State Fermentation

Polygalacturonases are enzymes involved in the degradation of pectic substances, being extensively used in food industries, textile processing, degumming of plant rough fibres, and treatment of pectic wastewaters. Polygalacturonase (PG) production by thermophilic fungus Thermoascus aurantiacus on solid-state fermentation was carried out in culture media containing sugar cane bagasse and orange bagasse in proportions of 30% and 70% (w/w) at 45°C for 4 days. PG obtained was purified by gel filtration and ion-exchange chromatography. The highest activity was found between pH 4.5 and 5.5, and the enzyme preserved more than 80% of its activity at pH values between 5.0 and 6.5. At pH values between 3.0 and 4.5, PG retained about 73% of the original activity, whereas at pH 10.0 it remained around 44%. The optimum temperature was 60–65°C. The enzyme was completely stable when incubated for 1 hour at 50°C. At 55°C and 60°C, the activity decreased 55% and 90%, respectively. The apparent molecular weight was 29.3 kDa, K m of 1.58 mg/mL and V max of 1553.1 μmol/min/mg. The presence of Zn+2, Mn+2, and Hg+2 inhibited 59%, 77%, and 100% of enzyme activity, respectively. The hydrolysis product suggests that polygalacturonase was shown to be an endo/exoenzyme.

Production of cellulolytic and hemicellulolytic enzymes from Aureobasidium pulluans on solid state fermentation

This article investigates a strain of the yeast Aureobasidium pullulans for cellulase and hemicellulase production in solid state fermentation. Among the substrates analyzed, the wheat bran culture presented the highest enzymatic production (1.05 U/mL endoglucanase, 1.3 U/mL β-glucosidase, and 5.0 U/mL xylanase). Avicelase activity was not detected. The optimum pH and temperature for xylanase, endoglucanase and β-glucosidase were 5.0 and 50, 4.5 and 60, 4.0 and 75°C, respectively. These enzymes remained stable between a wide range of pH. The β-glucosidase was the most thermostable enzyme, remaining 100% active when incubated at 75°C for 1 h.

Production of α-amylase by solid state fermentation by Rhizopus oryzae

A thermotolerant strain of Rhizopus oryzae was grown in three agro-industrial by-products: brewers’ rice, corn grits and wheat bran. Different substrates, cultivation time, moisture content, additional nitrogen sources, pH and temperature of incubation were evaluated aiming to optimize growing conditions. The highest enzymatic activity was observed after 24 h of cultivation using wheat bran as substrate with the following salt solutions: NH 4 NO 3 , MgSO 4 .7H 2 O and (NH 4 ) 2 SO 4 0.1% at temperature of 35°C. It was observed that changes in the pH range 4.0-6.0 did not significantly affect α-amylase activity. The optimum operation conditions were 75°C and pH 4.5. The enzymes remained stable at 75°C in the absence of substrate for 25 min. Key words: Starch hydrolysis, fermentation parameters, amylolytic enzyme.

QUALIDADE MICROBIOLÓGICA DE LEITE CRU REFRIGERADO OBTIDO DE PROPRIEDADES RURAIS DO MUNICÍPIO DE FRUTAL-MG: COMPARAÇÃO DAS ORDENHAS MECÂNICA E MANUAL

O objetivo deste trabalho foi avaliar a qualidade microbiologica do leite cru refrigerado obtido de propriedades rurais do municipio de Frutal/MG, com dois tipos de ordenha (mecânica e manual). Foram feitas analises de mesofilos totais, psicrotroficos e coliformes totais e termotolerantes. Para mesofilos totais, os resultados variaram entre 7,9 x 10 3 a 2,2 x 10 5 UFC.mL -1 no leite proveniente da ordenha manual, e entre 7,9 x 10 3 a 6,4 x 10 4 UFC.mL -1 da ordenha mecânica. Na contagem de psicrotroficos, apenas a primeira coleta do leite da ordenha mecânica apresentou esse tipo de micro-organismo, com valor de 1,85 x 10 2 UFC.mL -1 , enquanto que na ordenha manual houve contagens na primeira e ultima coleta, com valores entre 2,5 x 10 2 a 1,3 x 10 3 UFC.mL -1 . Com relacao a presenca de coliformes, foram verificadas contagens mais elevadas na propriedade de ordenha mecânica, na qual houve presenca de coliformes totais em todas as coletas, com resultados entre 4,3 x 10 2 a 4,6 x 10 3 NMP.mL -1 . Quatro amostras apresentaram coliformes termotolerantes, com valores entre 9,3.10 2 a 1,1.10 4 NMP.mL -1 . Na propriedade com ordenha manual, houve presenca de coliformes totais em duas amostras, com valores entre 9,2 x 10 1 a 4,6 x 10 3 NMP.mL -1 , as quais tambem apresentaram coliformes termotolerantes, com contagens entre 2,3.10 2 a 4,3.10 2 NMP.mL -1 . Todos os valores para mesofilos e psicrotroficos estavam dentro dos padroes exigidos pela legislacao. Ja para os coliformes, apesar de nao haver padrao estabelecido para leite cru refrigerado, as altas contagens podem indicar deficiencias nas praticas de higiene na ordenha.