Concomitant production of two proteases and alpha-amylase by a novel strain of Bacillus subtilis in a microprocessor controlled bioreactor

We describe the simultaneous production of Bacillus subtilis based proteases and alpha amylase using a computer controlled laboratory scale 7.5 L batch bioreactor. The present strain is the first to be reported that concomitantly produces these two industrially important enzymes. The growth and sporulation of Bacillus subtilis was monitored and maximum production of alkaline protease and alpha amylase was found to coincide with maximum sporulation. Two types of proteases were detected in the fermentation broth; a neutral and an alkaline protease most active in a pH range of 7.0-8.0 and 8.0-10, respectively. Maximum production of proteases was observed at an incubation temperature of 37ºC while that of alpha amylase was observed at 40ºC. The optimum aeration and agitation levels for protease production were 0.6 L/L/min and 200rpm, respectively, and for alpha amylase were 0.6 L/L/min and 150 rpm. The kinetic parameters Yp/x and qp were also found to be significant at the given fermentation conditions.

Comparison of solubility of zinc phosphate and glass ionomer cement in artificial saliva of varying pH values [in vitro study]

The aim of this study was to compare the solubility of Zinc Phosphate and Glass lonomer cements [conventional] in artificial saliva of different pH values. These cements are commonly used for permanent cementation of indirect restorations in dental practice at Peshawar, Pakistan and have to resist the harsh environment of oral cavity. The study was carried out at National Center of Excellence in Physical Chemistry, University of Peshawar, Pakistan. Both cements were mixed per manufacturer's directives to achieve excellent properties while using these as luting material. A total of 100 specimens were made for each dental cement and weighed prior to placement inpH medium of 2.46, 3.15, 3.56, 4.96 and 6.57 for 96 hours at 37°C temperature. After removal specimens were washed with doubly distilled water, dried in open air for 48 hours and reweighed. Percentage of solubility at each time period was calculated as 100 percent times weight loss divided by the initial weight of the specimen. It was found that the glass ionomer cement presented the highest solubility at low pH medium but was less soluble at high pH medium