Preliminary study on soil microbiota degrading plant latices and their protease and lipase enzymes

The present study aimed to isolate soil microorganisms-degrading plant latices and to screen their capablilities of producing protease and lipase. Many bacterial and fungal strains of mesophilic, thermotolerant or thermophilic nature were able to grow on sugar-free medium amended with crude latex of either Euphorbia pulcherrima, Ficus elastica or F. nitida and incubated at 25oC, 36oC or 45oC. This growth revealed that these growing microorganisms were able to make use of the crude latex as a sole carbon source. The total mesophilic bacterial propagules recovered on mineral salt medium amended with F. elastica latex was much higher than those recovered on media amended with either E. pulcherrima or F. nitida latex. Some of the mesophilic bacteria formed clear zones around their colonies (some Streptomyces spp. recovered on Ficus elastica and F. nitida latices) while the others showed no clear zones. Also one thermophilic and another thermotolerant species related to the genus Bacillus were isolated on media amended with the three plant latices. The total numbers of mesophilic fungal propagules recovered on medium amended with either Ficus latex were nearly equal, but higher than that amended with E. pulcherrima latex. Thirty-one species of fungi were recovered on the three latex media. Of mesophiles, Aspergillus followed by Fusarium, Penicillium and Cladosporium were the most common fungi, while the remaining fungi were less frequent. Three truly thermophilic species, Humicola grisea var. thermoidea, Malbranchea cinnamomea and Myceliophthora thermophile, were isolated. All mesophilic bacterial isolates, except one related to Streptomyces sp., were capable of producing protease and lipase, while from the thermophilic/thermotolerant bacterial isolates tested, only one Bacillus isolate could produce both enzymes and the other two isolates of Bacillus could not. The thirty mesophilic fungal isolates tested were capable of producing lipase, while 25 only were protease producers. On the other hand, the eleven thermophilic fungal isolates tested were capable of producing protease, while 8 only were lipase producers.