No abstract

Optimization of exopolysaccharides (EPS) produced by three strains of entomopathogenic fungi (Beauveria bassiana BCC 2692, Ophiocordyceps dipterigena BCC 2073, and Paecilomyces tenuipes BCC 2656) was carried out together with analyses of their prebiotic properties. B. bassiana BCC 2692 produced 6.27±0.22 g/L EPS on optimal medium using two-level fractional factorial design and 4.7 g/L EPS in bioreactor. EPS productions of O. dipterigena BCC 2073 were 13.2 g/L and 41.2 g/L in shake flask and bioreactor, respectively. For P. tenuipes BCC 2656, 1.47±0.21 g/L EPS in shake flask and 28.1 g/L EPS in bioreactor were obtained. These EPS were previously characterized as glucan with differences in molecular weights and degree of branching. They were resistant to hydrolysis by both hydrochloric acid and porcine pancreatic α-amylase. Furthermore, when used as the sole carbon source, all three types of EPS supported growth in vitro of two different probiotic bacteria (Lactobacillus acidophilus BCC 13839 and bifid bacterium animals ATCC 25527). A constant viability of L. acidophilus BCC 13839 was maintained throughout the cultivation period (48 hours) on all three entomopatogenic fungal EPS. All EPS also supported better growth and maintained longer growth period of B. animalis ATCC 25527 than glucose or inulin. Thus these entomopathogenic fungi EPS are promising candidates in prebiotic industry, expanding the pool of current commercial prebiotics.