RESUMEN
ABSTACT: The objective of this work was to isolate the polygalacturonase genes of Galactomyces citri-aurantii IJ-1 harvested from rotten citrus peels and to heterologously express these genes in Pichia pastoris. Two polygalacturonase (PG) genes from G. citri-aurantii IJ-1 were obtained and tentatively named PG1 and PG2. The genes were cloned into pPICZαC, and expressed in Pichia pastoris strain GS115 with a native signal peptide or the α-factor secretion signal peptide of Saccharomyces cerevisiae. All of the recombinant proteins were successfully secreted into the culture media and confirmed as a single band with a molecular weight of 35 to 38 kDa by SDS-PAGE. The specific enzyme activities of recombinant PG1 and PG2 purified by His-tag affinity resin were 4,749 and 6,719 U/mg, respectively, with an optimal pH and temperature of pH 4.0 and 50°C. The Michaelis-Menten kinetic constants for PG1 and PG2, K (m), were confirmed to be 0.94 and 0.84 mM, respectively. In the presence of Mn(2+), the activity of PG1 and PG2 were increased to 160.8 and 146.4% of normal levels, respectively. In contrast, Cu(2+) and Fe(3+) acted as strong inhibitors to the PGs.
Asunto(s)
Citrus/microbiología , Proteínas Fúngicas/genética , Expresión Génica , Pichia/genética , Poligalacturonasa/genética , Saccharomycetales/enzimología , Secuencia de Aminoácidos , Clonación Molecular , Frutas/microbiología , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismo , Concentración de Iones de Hidrógeno , Cinética , Datos de Secuencia Molecular , Pichia/metabolismo , Enfermedades de las Plantas/microbiología , Poligalacturonasa/química , Poligalacturonasa/metabolismo , Saccharomycetales/genética , Saccharomycetales/aislamiento & purificación , Alineación de Secuencia , TemperaturaRESUMEN
This study was carried out to investigate the isolation and characterization of lactic acid bacteria (LAB) from naturally fermented sauce-type kimchi. Sauce-type kimchi was prepared with fresh, chopped ingredients (Korean cabbage, radish, garlic, ginger, green onion, and red pepper). The two isolated bacteria from sauce-type kimchi were identified as Pediococcus pentosaceus and Lactobacillus brevis by 16S rDNA sequencing and tentatively named Pediococcus sp. IJ-K1 and Lactobacillus sp. IJ-K2, respectively. Pediococcus sp. IJ-K1 was isolated from the early and middle fermentation stages of sauce-type kimchi whereas Lactobacillus sp. IJ-K2 was isolated from the late fermentation stage. The resistance of Pediococcus sp. IJ-K1 and Lactobacillus sp. IJ-K2 to artificial gastric and bile acids led to bacterial survival rates that were 100% and 84.21%, respectively.
RESUMEN
Lactobacillus spp., referred to as IJ-1 and IJ-2, were isolated from the feces of breast-feeding piglets and analyzed for probiotic properties. According to the analyses of 16S rDNA sequence, Lactobacillus sp. IJ-1 showed greater than 99% homology with Lactobacillus reuteri DSM 20016(T), and Lactobacillus sp. IJ-2 had greater than 99% homology with the L. gasseri ATCC 33323(T) and L. johnsonii ATCC 33200(T). The pH changes in the culture media of Lactobacillus sp. IJ-1 and Lactobacillus sp. IJ-2 were from 6.5 to 4.2 and 4.6, respectively. Their respective resistance against artificial gastric acid and artificial bile acid led to survival rates of nearly 186+/-44% and 13+/-5%. Neither strain produced the carcinogenic enzyme beta-glucuronidase. Both strains inhibited the growth of pathogenic microorganisms, such as Listeria monocytogenes ATCC 19111, Salmonella enterica KCTC 12401, Salmonella enteritidis ATCC 13076, Staphylococcus aureus KCTC 3881, and Bacillus cereus 3711, within 24 h of growth.