This study describes the selection of an economical
medium for the growth and protease production by B.
cereus BG1 strain. This medium is based on low-cost
sardinelle powder. Among all the three sardinelle powders
tested, CHVSP supplemented with calcium chloride provided
the highest protease production level, followed by WSP.
However, the production of protease was significantly low
when the strain was cultivated in medium containing MSP.
The highest protease production (8,473 U/ml) in medium
containing 20 g/l CHVSP and 1 g/l CaCl2 indicates that the
strain can obtain its carbon, nitrogen and salts requirements
directly from sardinelle heads and viscera substrate.
The high level of protease activity obtained in the
presence of substrate prepared from whole sardinelle or
from heads and viscera, compared to that obtained with
meat sardinelle powder, could be due to the presence of
bioactive compounds in heads and/or viscera acting as
protease inducers. Further works are necessary to characterize
bioactive molecules present in heads or viscera sardinelle.
The high protease production obtained with cheap
product such as fish powders clearly indicated that these
substrates could be used in industrial fermentation
processes. Furthermore, using medium containing only
powder, obtained from fish processing by-products as
growth substrate, may reduce considerably the cost of
protease production.
The produced protease by B. cereus BG1 was stable in
neutral pH buffers and had a hydrolysis specificity for
casein.