Entomopathogenic Potential of <em>Bacillus velezensis</em> CE 100 for the Biological Control of Termite Damage in Wooden Architectural Buildings of Korean Cultural Heritage

Abstract

Biocontrol strategies are gaining tremendous attention with the growing awareness of the irreparable harm caused by the continuous use of synthetic pesticides. This study examines the proteolytic and chitinolytic activities of Bacillus velezensis CE 100 and its termiticidal effect through cuticle degradation. The proteolytic and chitinolytic activities of B. velezensis CE 100 systematically increased with cell growth to the respective peak of 68.3, and 128.3 units/mL after seventh days of inoculation, corresponding with the highest cell growth of 16 x 107 colony forming units (CFU)/mL. The in vitro termiticidal assay showed that B. velezensis CE 100 caused a rapid and high rate of termite mortality with the median lethal time (LT50) of &amp;amp;gt; 1h, and the highest mortality rate of 91.1% and 92.2% recorded at 11h and 12h in the bacterial broth culture and crude enzyme fraction, respectively. In addition to broken setae and deformed sockets, termites treated with the bacterial broth culture exhibited degraded epicuticles, while the crude enzyme fraction caused severe disintegration of both the epicuticle and endocuticle. These results indicate a tremendously higher prospect of B. velezensis CE 100 in the biological control of subterranean termites compared to the previously used entomopathogenic bacteria.