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Fibrinolytic enzyme genes (aprE2, aprE176, and aprE179) were introduced into the Bacillus subtilis 168 chromosome without any antibiotic resistance gene. An integration vector, pDG1662, was used to deliver the genes into the amyE site of B. subtilis 168. Integrants, SJ3-5nc, SJ176nc, and SJ179nc, were obtained after two successive homologous recombinations. The integration of each fibrinolytic gene into the middle of the amyE site was confirmed by phenotypes (Amy(-), Spec(S)) and colony PCR results for these strains. The fibrinolytic activities of the integrants were higher than that of B. subtilis 168 by at least 3.2-fold when grown in LB broth. Cheonggukjang was prepared by inoculating each of B. subtilis 168, SJ3-5nc, SJ176nc, and SJ179nc, and the fibrinolytic activity of cheonggukjang was 4.6 ± 0.7, 10.8 ± 0.9, 7.0 ± 0.6, and 8.0 ± 0.2 (U/g of cheonggukjang), respectively at 72 h. These results showed that construction of B. subtilis strains with enhanced fibrinolytic activities is possible by integration of a strong fibrinolytic gene via a marker-free manner.

A gamma-aminobutyric acid (GABA)-producing microorganism was isolated from jeot-gal (anchovy), a Korean fermented seafood. The isolate, A156, produced GABA profusely when incubated in MRS broth with monosodium glutamate (3% (w/v)) at 37°C for 48 h. A156 was identified as Lactobacillus sakei by 16S rRNA gene sequencing. The GABA conversion yield was 86% as determined by GABase enzyme assay. The gadB gene encoding glutamate decarboxylase (GAD) was cloned by PCR. gadC encoding a glutamate/GABA antiporter was located immediately upstream of gadB. The operon structure of gadCB was confirmed by RT-PCR. gadB was overexpressed in Escherichia coli BL21(DE3) and recombinant GAD was purified. The purified GAD was 54.4 kDa in size by SDS-PAGE. Maximum GAD activity was observed at pH 5.0 and 55°C and the activity was dependent on pyridoxal 5'-phosphate. The Km and Vmax of GAD were 0.045 mM and 0.011 mM/min, respectively, when glutamate was used as the substrate.

Bacillus subtilis HK176 with high fibrinolytic activity was isolated from cheonggukjang, a Korean fermented soyfood. A gene, aprE176, encoding the major fibrinolytic enzyme was cloned from B. subtilis HK176 and overexpressed in E. coli BL21(DE3) using plasmid pET26b(+). The specific activity of purified AprE176 was 216.8 ± 5.4 plasmin unit/mg protein and the optimum pH and temperature were pH 8.0 and 40°C, respectively. Error-prone PCR was performed for aprE176, and the PCR products were introduced into E. coli BL21(DE3) after ligation with pET26b(+). Mutants showing enhanced fibrinolytic activities were screened first using skim-milk plates and then fibrin plates. Among the mutants, M179 showed the highest activity on a fibrin plate and it had one amino acid substitution (A176T). The specific activity of M179 was 2.2-fold higher than that of the wild-type enzyme, but the catalytic efficiency (kcat/Km) of M179 was not different from the wild-type enzyme owing to reduced substrate affinity. Interestingly, M179 showed increased thermostability. M179 retained 36% of activity after 5 h at 45°C, whereas AprE176 retained only 11%. Molecular modeling analysis suggested that the 176(th) residue of M179, threonine, was located near the cation-binding site compared with the wild type. This probably caused tight binding of M179 with Ca(2+), which increased the thermostability of M179.

LAB were isolated from makgeolli locally produced around Jinju, Gyeongnam, S. Korea during spring of 2011. Randomly selected 11 isolates from MRS agar plates were identified first by API CHL 50 kits and then 16S rRNA gene sequencing. All 11 isolates were identified as Lactobacillus plantarum. Among them, ST4 grew in MRS broth with ethanol up to 10%, showing the highest alcohol resistance. L. plantarum ST4 was moderately resistant against acid and bile salts. When cellular proteins of L. plantarum ST4 under ethanol stress were analyzed by two-dimensional gel electrophoresis (2DE), the intensities of 6 spots increased, whereas 22 spots decreased at least 2-fold. Those 28 spots were identified by peptide mass fingerprinting (PMF). FusA2 (elongation factor G) increased 18.8-fold (6% ethanol) compared with control. Other proteins were AtpD (ATP synthase subunit beta), DnaK, GroEL, Tuf (elongation factor Tu), and Npr2 (NADH peroxidase), respectively. Among the 22 proteins decreased in intensities, lactate dehydrogenases (LdhD and LdhL1) were included.

A 2.5 kb aga gene encoding alpha-galactosidase (alpha- Gal) from Leuconostoc mesenteroides SY1 was cloned into pSJE, an E. coli-Leuconostoc shuttle vector. The recombinant plasmid, pSJEaga, was introduced into Leuconostoc citreum KCTC3526 (ATCC49370) by electroporation. Transcription level of aga was the highest in cells grown on raffinose (1%, w/v) followed by cells grown on galactose, melibiose, fructose, glucose, and sucrose. Western blot using antibodies against alpha-Gal showed similar results to slot-blot results and enzyme activity measurements. All the results indicated that the heterologous aga was successfully expressed in L. citreum and its transcription was under the carbon catabolite repression (CCR).