TITLE:
Solid-State Fermentation for the Concomitant Production of δ-Endotoxin and Endospore from Bacillus thuringiensis subsp. kurstaki
AUTHORS:
Veloorvalappil Narayanan Jisha, Sailas Benjamin
KEYWORDS:
Bacillus thuringiensis subsp. kurstaki, Spore, Solid-State Fermentation, δ-Endotoxin
JOURNAL NAME:
Advances in Bioscience and Biotechnology,
Vol.5 No.10,
September
12,
2014
ABSTRACT: Water stress and limited aeration imparted by solid-state fermentation
(SSF) were reported as crucial factors for the enhancement of endospore
production by Bacillus thuringiensis (Bt); and thus, more δ-endotoxin
could be produced concomitantly with reduced time. Therefore, Bt subsp. kurstaki (Btk) was
employed in the present study to evaluate its efficiency for the concomitant
production of endospores and δ-endotoxin
in LB medium supplemented with various naturally available agricultural
products, i.e., flours of soybean,
Bengal gram or jack seed at various concentrations (10%, 20%, 30%, 40%, 50%, 60%,
80% or 100%, all w/v). After 12 h fermentation, the supernatant in it was
centrifuged off aseptically to obtain solid substrate for subsequent SSF. Of
them, soybean (30%) supplemented medium was the best
for the enhanced production of endospore and δ-crystals. The maximum yield of endospores during solid-state
fermentation was observed 48 h, i.e.,
compared to submerged fermentation in LB, it was 24 h less gestation period. In control sample, the endospores achieved the
maximum length (1.10 ± 0.13 μm) and
diameter (0.63 ± 0.07 μm) at 72
h; while in soybean supplemented medium, the maximum length (2.10 ± 0.16
μm) and diameter (1.63 ± 0.16 μm) were at 48 h and 72 h, respectively. Upon
staining, acridine orange specifically stained the endospores; malachite
green-saffranin stained both δ-crystals and endospores; and coomassie
brilliant blue specifically stained δ-endotoxin. Briefly, normal gestation
period or harvest time for Btk is 72 h, which could be reduced to 48 h,
if SSF is employed as demonstrated in this study.