Protease F1, a thermostable alkaline protease extracted from Bacillus
stearothermophilus strain F1 was investigated for its soil removing properties. In this
study the general purity of crude Protease F1 was first determined. Protease F1 was
found to be free of lipase, cellulase and a.-amylase activities.
The washing performance of crude Protease F1 was measured in terms of
percentage soil removal and compared to a commercial enzyme, Savinase. The effects
of various factors such as types of soil, washing temperature, enzyme activity, water
hardness, pH, types of surfactants and builders on the washing performance of
Protease F1 were measured.
The washing performance was determined by stirring a type of soiled cloths in
1 liter solution of enzyme (with a fixed amount of activity) for 10 minutes, followed
by 2x3 minutes rinsing. The difference in the whiteness of the soiled cloth before and
after washing indicate the degree of soil removal (or detergency). Among the various types of soiled cloth studied, the one soiled with oil, pigment and milk (AS12) gave a better contrast when washed by the enzymes than the cloihs soiled by btood or the
egg.
Protease Fl washed better than Savinase at an the temperatures studied. The
difference in performance was found to be greatest at 70˚C. washing efficacy was
found to increase with increase in concentration of the enzymes lUl1il a certain level
beyond which a drop in the percentage soil removal was observed. The enzymes
performed better at lower water hardnesses. Generally Protease F1 was more sensitive
to water hardness than Savinase. At room temperature (RT) and 50˚C, Savinase
performed better at all pH's. However, at 70°C and pH 7 and 8, Protease F1
performed better.
When formulated with surfactants or builders, Protease Fl was found to
enhance the performance of surfactants while Savinase, the builders. The best
washing performance was when enzymes, surfactant and builders were formulated
together and the washings carried out at RT and 50˚C
