Distribution Of Yeasts In Wastewater Treatment Systems And Theirenzyme Producing Characteristics

Although the abundance of yeasts in the activated sludge of a wastewater treatment system was low,hey might havesome ecological functions. In our research group, the molecular ecology of yeasts in variouswastewater treatment systems was widely investigated. Based on the previous studies, the distribution ofyeasts in printing and dyeing, and antibiotics fermentation wastewater treatment systems were furtherstudied through isolation and cultivation methods. Their characteristicsof producitn extracellular enzymes,lipids and glycolipids were detected. The following results were obtained.1. Eighty-four yeast isolates were obtained from the two wastewater treatment systems. They wereclassified in20species of10genera mainly distributing in Candida sp. and Rhodotorula sp.. The genusCandida was the most dominant populationin the printing and dyeing wastewater treatment systemoccupying33.3%of the total yeast isolates; the genus Rhodotorula was the most dominant populationin theantibiotics fermentation wastewater treatment systems occupying35.42%of the total yeast isolates.2. The abilities of yeast isolates to produce different extracellular enzymes were studied. The resultsindicated that of the84yeasts,10,4and34produced lipase, protease and manganese dependant peroxidase(MnP), respectively. The lipase producing yeasts fell in Torulaspora delbrueckii, Cryptococcus curvatus,Rhodotorula mucilaginosa, Candida parapsilosis, Candida rugosa and some unidentifiedSaccharomycetales. The4protease producing yeasts were identified as Rhodotorula mucilaginosa andTorulaspora delbrueckii. After cultivated in liquid medium for36hours, AA-M12(Rhodotorulamucilaginosa), AA-Y5(unidentified Saccharomycetales) and AA-M17(Candida rugosa) were shown tohave the highest activities of protease, lipase reaching8.24U/ml,2.5U/ml and2.5U/ml, respectively.AA-M12(Rhodotorula mucilaginosa) could simultaneously produce lipase and protease. AA-Y5(unidentified Saccharomycetales) and AA-Y36(unidentified Saccharomycetales) could simultaneouslyproduce lipase and MnP.3. Under the conditions of reactive red M-3BE presence,34yeast isolates could produce MnP mainlydistributing in Candida, Trichosporon and Rhodotorula. DA-M26(Candida parapsilosis) and AA-Y32(Candida tropicalis) could produce the highest activitiesof MnP reaching1115.385U/L and692.3011U/Lat cultivated in liquid medium for36hours. The abilities of dyes decolorization by the yeast isolates were researched. The results indicated that78of the84yeast isolates had the abilities of decolorizing reactivered, of which the decolorization rates of48strains exceeded90%.