One of the obstacles in the way of wide scale industrial application of biosurfactants is the high production cost coupled with a low production rate. In order to lower the production cost surfactin production by Bacillus subtilis MTCC 2423 was studied in submerged batch cultivation using waste frying oils. It was observed that the decrease in surface tension was 56.32%, 48.5% and 46.1% with glucose, waste frying sunflower oil and waste frying rice bran oil, respectively. Biomass formation was 4.36 g/L, 3.67 g/L and 4.67 g/L for glucose, waste frying sunflower oil and waste frying rice bran oil, respectively. Product yield (g product/g substrate) was 2.1%, 1.49% and 1.1% with glucose, waste frying sunflower oil and waste frying rice bran oil as substrates. This process facilitates safe disposal of waste frying oil, as well reducing the production cost of surfactin.

Coolants are widely used in industries for metal cutting operations. Though there are varieties of coolants available, the most widely used are water-soluble coolants because of their low cost and better heat dissipation compared to straight cutting oils. In the present investigation, amongst the various causes, which deteriorate the coolant, the role of hardness of water is primarily studied. Accordingly, water from different sources with varying hardness is considered and coolants are prepared from the same. The extent to which hardness can affect the performance of coolants is studied as a function of coolant lubricity in a reciprocating tribometer. Further, the effect of entry of coolants into lubricated machine tool slideways is also assessed by evaluating the mixture of coolant and lubricating oil for its frictional behavior. This is important from assessing the impact of the mixing of coolant and lubricating oil on machine tool slideways with regard to positioning exactness and stick slip behavior of slideways in terms of coolant-lube compatibility.