Abstract
BACKGROUND: The search for sources of industrial biocatalysts, which are non-pathogenic and can utilise cheap nutrient sources, has been a continuous endeavour in the ~ 7 billion USD enzyme industry. Beauveria bassiana, an endophytic fungal entomopathogen, is non-pathogenic and possesses the potential to secrete various bioproducts while utilising readily available lignocellulosic biomass. OBJECTIVE: This study investigated the optimised production of two glycosyl hydrolases, amylase and polygalacturonase, by B. bassiana while utilising readily available agricultural residues. Subsequently, the industrial potential of the enzymes in the clarification of fruit juice was evaluated. MATERIALS AND METHODS: Initially, seven agro residues were screened for the concomitant production of amylase and polygalacturonase by B. bassiana SAN01. Subsequently, statistical optimisation tools, Plackett Burman Design (PBD) and Central Composite Design (CCD), were employed for the optimisation of enzyme production. The enzyme mixture was partially purified and applied in the clarification of pineapple juice. RESULT: The production of B. bassiana SAN01 amylase and polygalacturonase was found to be maximal while utilising wheat bran. Subsequent to PBD and CCD optimisation, the optimal conditions for enzyme production were identified to be at 30 °C, pH 6.0 and wheat bran concentration of ~40 g.L(-1). Under these optimised conditions, heightened production levels of 34.82 and 51.05 U.mL(-1) were recorded for amylase and polygalacturonase, respectively, which were 179% and 187% of the initial unoptimised levels. In addition, the most effective clarification of the juice (~90%) was observed at 35 °C after an incubation time of 120 min with no significant effect on the pH and total dissolved solids. CONCLUSION: B. bassiana, a well-known biocontrol agent, was shown to produce amylase and polygalacturonase using readily available agricultural residues for the first time. These enzyme production levels are the highest for these enzymes from any known endophytic fungal entomopathogen. This study further demonstrates the potential applicability of B. bassiana in other industrial processes besides its widespread use as a biopesticide.