Production of Paecilomyces fumosoroseus conidia in submerged culture

Mexican isolates of Paecilomyces fumosoroseus (Wize) Brown & Smith virulent to nymphs and adults of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) were screened in terms of spore production in submerged culture. Effects of light, temperature stress and yeast extract on sporulation were studied. Cycles of 12 hours light/12 hours dark increased spore production as well as an incubation for 24 hours at 37 degrees C prior to incubation at 30 degrees C. Ln absence of organic nitrogen both fungal growth and sporulation were very low. Spore production in fermenters with a culture media of a C:N ratio of 25 was doubled as compared to a media with a C:N ratio of 11. Both conidia and blastospores were produced. Production of conidia directly from blastospores through microcyclic sporulation was observed. The proportion of conidia obtained under optimal conditions was 88.8%. Submerged culture of P. fumosoroseus seemed advantageous compared to rice-filled plastic bags production method because of shorter fermentation times, higher spore yields and substantially higher volumetric spore productivity. Results indicated that careful manipulation of nutritional and environmental conditions allowed for production of conidia during submerged growth of P. fumosoroseus, microcyclic sporulation being induced under a set of environmental conditions including temperature stress and nutrients limitation.