Produção da enzima ciclodextrina glicosiltransferase por Bacillus sp. imobilizados em quitosana

• Autor(a) principal: Es, Ismail
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• dARK ID: ark:/38995/00130000034xs
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/5556
• topic: CGTase; Imobilização de biocatalisador; Cultura batelada; Quitosana; Bacilo; CGTase; Biocatalyst immobilization; Batch culture; Chitosan; Bacillus; CIENCIAS BIOLOGICAS::GENETICA

Production of a starch-degrading cyclodextrin glicosiltransferase (CGTase, EC 2.4.1.19) on solid-state culture and batch fermentation was evaluated by free and immobilized alkalophilic Bacillus sp on polymeric chitosan matrix. Immobilization procedure was performed by mixing bacterial cells with low molecular weight chitosan dissolved in HCl. Structure of free bacterial cell, polymeric chitosan matrix and immobilized cells were visualized by scanning electron microscopy (SEM). The images obtained from SEM showed that the procedure used for immobilization was easy, cheap and effective. Three different starch sources as substrate were used: potato, corn and cassava. Qualitative analysis of CGTase production was determined by colorless area formation on solid culture containing phenolphthalein. Enzymatic indices, which indicated the production of CGTase on solid culture, were calculated for both free and immobilized cells on different starch sources. Enzyme activity of CGTase was determined before and after each purification step: ammonium sulfate precipitation, starch adsorption and dialysis. Biomass growth and substrate consumption were analyzed by Flow cytometry and modified phenol-sulfuric acid assay, respectively. Free cells reached very high numbers (2.5 × 107 ml-1) during batch culture, besides; immobilized cells maintained initial inoculum concentration (2.5 × 105 ml-1) during enzyme production. The maximum enzyme activity achieved by free cells was 21.25 U (35 h), 14.65 U (40 h) and 19.16 U (33 h) on cassava, potato and cornstarch, respectively. During batch culture, immobilized cells produced CGTase with the enzyme activity of 24.375 U (16 h) for cassava, 24.375 U (9 h) for potato starch and 21.25 U (8.5 h) for cornstarch in a shorter cultivation time. Consequently, immobilization decreased the production time and increased enzyme activity of CGTase.