Use of Trichoderma koningiopsis chitinase to enhance the insecticidal activity of Beauveria bassiana against Diatraea saccharalis

Trichoderma is a well-known soil-borne fungus, highly efficient producer of extracellular enzymes including chitinases. The aim of this study was to recover a chitinase from fermentation waste after harvesting Trichoderma koningiopsis Th003 conidia and assess its potential as an enhancer of Beauveria bassiana insecticidal activity against Diatraea saccharalis. T. koningiopsis was produced by solid fermentation, conidia were harvested, and a crude extract (CE) was recovered by washing the residual substrate (rice:wheat bran). The partially purified chitinase (PPC) (75 kDa product) with N-acetyl-β-glucosaminidase activity was obtained by chromatography to 29.3-fold with optimal activity at pH 5 and 55°C. Both the CE and the PPC were mixed with B. bassiana Bv062 conidia and assessed in a bioassay against D. saccharalis larvae. The CE and PPC from T. koningiopsis Th003 did not affect the germination or viability of B. bassiana conidia and enhanced its insecticidal activity when used at 0.06 U/ml enzymatic activity with a 24.5% reduction in B. bassiana lethal time (LT₉₀). This study demonstrated the potential of chitinases produced by T. koningiopsis in solid fermentation to be recovered from the waste substrate and used as an additive to enhance B. bassiana, adding value to the main waste from the Trichoderma biopesticide/biofertilizer industries.     

Investigation of extracellular elastase, acid proteinase and phospholipase activities as putative virulence factors in clinical isolates of Aspergillus species

We investigated the production of extracellular elastase, acid proteinase and phospholipase enzyme activities in clinical isolates of Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger and any possible correlation between the existence of these enzymes and development of invasive aspergillosis. A total of 73 strains (45 A. fumigatus, 23 A. flavus, 5 A. niger) isolated from patients with invasive aspergillosis (n = 55), superficial aspergillosis (n = 5), allergic bronchopulmonary aspergillosis (n = 1), and from those colonized with Aspergillus (n = 12) were included in the study. The enzymatic activities were tested on solid media supplemented with the corresponding substrates. Elastase activity was detected in 95.6, 82.6, and 0% of A. fumigatus, A. flavus, and A. niger isolates, respectively. Acid proteinase activity was detected only for A. fumigatus and in 20 of 45 isolates belonging to this species. Phospholipase activity was present in all strains of A. fumigatus and A. niger but in none of the isolates of A. flavus. No statistical correlation could be established between the existence of elastase or acid proteinase activity and development of invasive disease (p > 0.05). While high phospholipase production was found to be associated with development of invasive aspergillosis (p < 0.01), not all isolates that caused invasive diseases showed high phospholipase activities.