Isolation, Identification Of Lipase Producing Strain And Elementary Researcment On De-inking

Biological deinking is one of the focuses of wastepaper recycle.Many studies and reports prove that lipase have important effect in the biological de-inking process. Lipase can decompose vehicle material of printing ink to release ink particle from firber. It can increase production efficiency and fiber intensity. So lipase may have promising application in wastepaper de-inking reproduction.In this study, 176 bacterial strains were isolated from the soil polluted by printing ink by method of enrichmental cultivating with mineral oil as its unique carbon source. One of the bacterial strains named LP502 with high enzyme activity was isolated. According to the strain morphology,colony character, physiological and biochemical experiments,it should belong to Acinetobacter. According to 16S rDNA gene and gyrB gene of LP502 sequences,it ccould be identified as Acinetobacter calcoaceticus.The specail lipase enzyme active dyeing proved that the enzyme could specially hydrolaze lipase substrate. Fermentation process was optimized. The optimized cultural medium of fermentation for lipase production was studied. The optimized cultural medium was constituted with: K2HPO4 0.1%,(NH4)2SO4 0.1%,peptone 3%, MgSO4.7H2O 0.1%,mineral oil 0.5%,sucrose 1%,beef extract 1%, The optimal intivital pH was 7.0,volume of substrate was 20mL,best temperature was 30℃.Under the optimized condition,Enzyme activity reached at 25000U/L afer fermentation for 72h. The enzyme was used for the old newsprinting paper de-inking. After flotating and sheeting, the brightness of reproduced paper was to 224.9513, which was 42.5315 higher than old newspaper without biological deinking. The results suggested that lipase of Acinitobacter calcoaceticus LP502 could make ink particle released from firber in the process of de-inking.A genomic DNA library of the strain LP502 has been constructed, which set a solid foundation for cloning of the lipase gene.