Abstract
The effect of culture conditions on protease production and bacterial growth of Bacillusclausii was investigated using Taguchi design of experiment. Five factors viz., carbon source, organic and inorganic nitrogen sources, agitation and metal ion, each at four levels were selected and an orthogonal array layout of L16 (45) were performed. The proposed medium for alkaline protease production consisted of (g/l): sucrose, 10; yeast extract, 10; KNO3, 5; trace element without Mn2+. Under these optimal conditions, 4 fold enhancement in protease production (from 250 to 1000 U/ml) was obtained. At the optimum culture for bacterial growth, which contained (g/l): starch, 10; yeast extract, 10; ammonium ions, 5; trace element without Zn2+, 1.88 fold increase in growth production (from OD600 nm of about 8.5 in basal medium to OD600 nm of 16 in optimized medium) were observed. The inorganic nitrogen source was the most significant factor on protease production with 57.75% contribution. The organic nitrogen and carbon sources by 35.28 and 34.93% contributions were prominent factors in bacterial growth. Key words: Alkaline protease, Bacillus clausii, medium optimization, taguchi method.
Highlights
Proteases constitute one of the most important groups of industrial enzymes, being extensively used in food, detergent, and other industries
Experiments study with the designed experimental condition showed significant variation in the protease activity (Table 2)
The analysis of variance (ANOVA) for two responses of protease production and bacterial growth were carried out according to the factors with the contribution more than 10% as suggested by software
Summary
Proteases constitute one of the most important groups of industrial enzymes, being extensively used in food, detergent, and other industries. Most of the available proteases produced commercially are of microbial origin. The alkaline proteases produced by Bacillus species are by far the most important group of enzymes produced commercially (Moon and Parulekar, 1991; Gupta et al, 2002). It is well established that extracellular protease production in microorganisms is greatly influenced by media components. The effect of various carbon and nitrogen nutrient cost-effective substrates, divalent metal ions, environmental and fermentation parameters such as pH, temperature, aeration, and agitation were evaluated in the literature (Adinarayana and Ellaiah, 2002; Varela et al, 1996). For optimization of all factors and establishment the best possible conditions by considering all interaction of parameters, numerous experiments have to be carried out, which is not economical and practical
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