Anti-α-glucosidase (AAG) compounds have received great attention due to their potential
use in treating diabetes. In this study, Bacillus licheniformis TKU004, an isolated bacterial strain
from Taiwanese soil, produced AAG activity in the culture supernatant when squid pens were
used as the sole carbon/nitrogen (C/N) source. The protein TKU004P, which was isolated from
B. licheniformis TKU004, showed stronger AAG activity than acarbose, a commercial anti-diabetic
drug (IC50 = 0.1 mg/mL and 2.02 mg/mL, respectively). The molecular weight of TKU004P,
determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), was 29 kDa.
High-performance liquid chromatography (HPLC) analysis showed that TKU004P may be a protease
that demonstrates AAG activity by degrading yeast α-glucosidase. Among the four chitinous sources
of C/N, TKU004P produced the highest AAG activity in the culture supernatant when shrimp head
powder was used as the sole source (470.66 U/mL). For comparison, 16 proteases, were investigated
for AAG activity but TKU004P produced the highest levels. Overall, the findings suggest that
TKU004P could have applications in the biochemical and medicinal fields thanks to its ability to
control the activity of α-glucosidase.