Four strains of Bacillus subtilis (M2, M14, M35 and M54) were selected
for production of protease enzyme and degumming of silk fibers. The data
revealed that, maximum protease activity and specific activity were obtained
by B. subtilis(M14) followed by B. subtilis(M54) when grown in Chopra and
Mathur medium at 30C for 5 days under shake culture conditions. When the
strains individually incubated in the medium supported with silk fiber, the loss
of the gum might amount to 30.56% with high total activity of protease in the
culture supernatants. Culture supernatants of four strains with high protease
activity were most effective in reducing the gum content of silk fibers within 4
hr and slightly increase within 8 and 16 hr. Four grams silk fiber per 100 ml
culture filtrate was the best ratio for the highest degumming by B. subtilis
M14, M35 and M54 strains while 3:100 (w/v) was the best ratio for
degumming by B. subtilis (M2). Degumming of silk fibers increased with the
using of crude enzyme of B. subtilis (M14) followed by (M54) and (M2) strains
at 30 C, while B. subtilis (M35) gave the highest silk degumming at 50C.
Results showed that, maximum degumming and total activity of protease have
been observed at pH 7.0 to all filtrates of the four strains. These results
indicated that, protease of B. subtilis plays an active role in the degumming of
silk fibers.