Effect of the milling of wheat bran on its properties and reactivity during biocatalytic conversion

Resumo

The possibility of using wheat bran as a feedstock for sugar production via biocatalytic conversion is demonstrated. The relatively low reactivity of this feedstock can be doubled or quadrupled by dry milling on an AGO-2S planetary mill activator. The maximum yield of reducing sugars, 68.6 g/L (initial substrate concentration, 100 g/L; glucose is the major component of the resulting sugars, 93–95%), is achieved when wheat bran milled for 7–10 min is subjected to bicatalytic conversion using the complex enzyme preparation (EP) of Penicillium verruculosum gaBG with cellulolytic, hemicellulolytic, and amylolytic activity at a gaBG dose of 60 mg/g (supplemented with F10 β-glucosidase EP, 40 units/g). Polysaccharides comprise 62.4% of the dry weight of the wheat bran; allowing for the water incorporated during enzymatic hydrolysis, the achieved yield is close to the theoretical figure (68.6 g/L) and there is virtually complete conversion of the wheat bran carbohydrates. Lengthening the duration of milling to 7–10 min considerably reduces the size of bran particles, lowers (by 28%) their ability to bind water, nearly doubles the content of water-soluble sugar, and increases (by 12.6%) the total content of soluble components, relative to the initial material.