Estudo da produção de amiloglicosidase por Aspergillus Niger NRRL 3122 em fermentação semi solida de farelo de arroz

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

This is an experimental study of solid-state fermentation(SSF) of rice bran to produce amyloglucosidase (E.C. 3.2.1.3.) by Aspergillus niger NRRL 3122. The research was conducted in 4 phases: optimization of physico-chemical parameters; SSF in fixed-bed column reactors; characterization of enzyme kinetics; determination of thermal conductivity. An experimental design strategy was employed for optimization and modelling of 6 variables: fermentation time, fermentation temperature, moisture, inert concentration, spore concentration and sterilization time. Experiments were conducted in flexible packs of polypropylene. The methodology involved the development of a Fractional Factorial Design, a Steepest Ascent Path and two Central Composite Designs. The most significant parameters were found to be the fermentation and sterilization times. The mathematical models presented a significance level of over 95%. The greatest values for the enzyme activity of non-purified mouldy bran were above 800 IU / gbran. The influence of aeration on enzyme production was determined for the packed-bed column fermenter, using flow rates of O to 150 mlair/h/gmedium. Highest values of enzyme activity were 1700IU/gbran and 60 mlair/h/gmedium. Fixed beds packed with 586 and 858 g/l did not influence on enzymatic activity or productivity. Temperature measurements within the bed showed a radial conduction mechanism as mainly responsible for dissipation of the metabolic heat generated. The thermal conductivity of the mouldy bran was represented by the model: k =47,5080 + 0,0115*dap+0,1295*U-6,0737*ln(dap) - 5, 5555*ln (U). Kinetcs experiments revelaled a Michaelis-Menten constant of 2,30 ~ 0,39 g/l, and maximum enzyme activity at 55°C and pH 4,6. Better stability was attained with pH 4,4. The deactivation energy was calculated to be 31,98 Kcal/gmol, and an equation was established for the thermal deactivation constant : Kd(h-1) = 8,0478 X 1020 e-16153/T.

ASSUNTO(S)

aspergilos amiloglicosidase fermentação farelo de arroz

ACESSO AO ARTIGO

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