Evaluation of cow dung as a cheap substrate for alkaline
protease production
This study has indicated that cow dung can be used as a
potential substrate for alkaline protease production. Enzyme
production by the B. subtilis strain VV was to the
tune of 4030 ± 128 U/g solid substrate (cow dung) after
72 h of incubation at 37°C. The selection of a cheap substrate
in SSF for the production of any metabolites is an important
factor from an industrial point of view. Apart from
the cost, the availability of the substrate is a critical factor.
An ideal substrate is one which is available in large quantities
and throughout the year too. Although many cheap
agro-industrial residues were evaluated (Prakasham et al.
2006; Johnvesly et al. 2002; Gessesse 1997) for the production
of alkaline proteases, the availability of these substrates
is seasonal. Apart from agro-industrial wastes, more attention
has been paid to the evaluation of solid wastes for the
production of alkaline proteases (Ravindran et al. 2011;
Ganesh Kumar et al. 2008). Waste water from the manufacture
of shochu was also tried (Morimura et al. 1994) for
production of proteases. In spite of evaluating these substrates,
the search for a novel substrate continues. Recently,
we used cow dung as a substrate for the production of a
halo-tolerant alkaline protease using a alkalophilic isolate,
Halomonas sp. PV1 (Vijayaraghavan and Vincent 2012). Of
all the alkalophilic microorganisms that have been screened
for use in various industrial applications, members of the
genus Bacillus were found to be predominant and a prolific
source of alkaline proteases (Kumar and Takagi 1999).
Reports on SSF of cow dung for the production of alkaline
protease using Bacillus sp. are limited or perhaps not available.
Hence, the present investigation aimed to exploit cow
dung that is cheap and globally available for alkaline protease
production by Bacillus subtilis. The protein content of
the cow dung medium was evaluated before and after fermentation.
The cow dung possessed 80 ± 12 mg protein/g
solid substrate, and the organism utilized 40 ± 4.5% of the
protein content for the growth and synthesis of protease.