TITLE:
Medium factors affecting extracellular protease activity by Bacillus sp. HTS 102—A novel wild strain isolated from Portuguese merino wool
AUTHORS:
Ana Catarina Queiroga, Manuela Estevez Pintado, Francisco Xavier Malcata
KEYWORDS:
Fractional Factorial Design; Thermotolerant Enzyme; Proteolytic Activity; Bacillus sp.; Ewe’s Wool
JOURNAL NAME:
Natural Science,
Vol.5 No.6A,
June
18,
2013
ABSTRACT: The synthesis of an
extracellular protease by Bacillus sp.
HTS102—a wild strain recently isolated from the wool of Portuguese Merino
ewes, was optimized. This protease is thermostable
and particularly resistant to harsh
environmental conditions—and appears to bear a unique ability to
hydrolyze keratin-rich solid materials. Following a preliminary screening for
the most relevant medium factors involved in processing, a fractional
factorial design (2VI6-1) was applied to ascertain the
effects of six relevant parameters—viz. yeast extract concentration, peptone
level, inoculum size, stirring rate, temperature and pH. The concentrations of
yeast extract and peptone, as well as the incubation temperature and pH were
found to play significant roles; and the 2-factor interaction between yeast
extract level and pH was also significant. A 2.2-fold increase in the overall
level of protease synthesis was eventually attained, with the improved medium
relative to the basal medium—which is noteworthy when compared with competing
proteases and previous optimization efforts.