SCREENING OF LIPASE-PRODUCING MICROORGANISMS ISOLATED FROM PUEBLA SOILS FOR TRANSESTERIFICATION OF WASTE COOKING OIL

Abstract

Thirty two lipase producing strains were isolated from different soils from Puebla City by employing conditioning culture techniques with media that contain waste cooking oil. The pH conditions were 5, 7 and 9, hence given a total of 9 independent cultures. The first screening and isolation criteria was carried out with samples of the liquid media inoculated in agar plates with same media composition and conditions as described above and 0.001% (w/w) of fluorescent dye Rhodamine B. The microbial growth was presented in all plates, however not all microbial colonies presented lipase activity evaluated as a result of a characteristic dark halos (fluorescent lost) observed under UV light (355 nm) due an association of Rhodamine B with esters formed by lipase transesterification and/or esterification reactions. Microorganisms with remarkable lipase activity were selected for further purification. In media with pH values of 7 have been isolated 5, 9 and 9 strains from CN, MM and MMS respectively. Seven strains for media at pH value of 5, corresponding to 3 from CN and 4 from MM. Only two strains were isolated in MMS at pH value of 9. In subsequent studies, isolated microorganism will be identified and their lipase activity will be quantified by transesterification reactions with waste cooking oils and methanol for Biodiesel production.