Protease extraction in solid state fermentation of wheat bran by a local strain of Rhizopus oryzae and growth studies by the soft gel technique

Studies on the extraction of protease in the solid state fermentation of wh eat bran by Rhizopus oryzae, were conducted. Using distilled water (DW) as extractant, the optimum volume was 5 ml/g bran. An extraction or soaking ti me of 2 h at 4 degrees C was sufficient to extract out nearly 90% (52.5 U/g bran) of enzyme while complete extraction was attained in 10 h (58.7 U/g b ran). With the optimum extractant Volume of 5 ml DW/g bran, most of the enz yme was recovered in one extraction (60 U/g bran) while repeated extraction s yielded very little enzyme (5 and 2.8 U/g bran in the second and the thir d extractions, respectively). An attempt has been made to explain these res ults with the leaching or dissolving equation. Among other studies, while e xtractant pH did not affect recovery, extraction with neutral potassium pho sphate buffer resulted in increased yields compared to DW and was also affe cted by the molarity of the buffer, with the maximum increase (1.42 times) being effected by 0.6 M buffer. Another major study was the investigation o f protease production in relation to growth as seen in 'soft gel culture'. Growth in soft gel culture was almost linear although colony growth on malt extract agar was radial. Production did not appear to be associated with g rowth. (C) 2000 Elsevier Science Ltd. All rights reserved.