Myoung Geun Yun

Novel multiplex PCR for the detection of lactic acid bacteria during kimchi fermentation

We developed a multiplex PCR assay for the detection of lactic acid bacteria (LAB) species, and used it to examine the LAB species involved in kimchi fermentation. The LAB profile during kimchi fermentation varied with pH and acidity. Leuconostoc mesenteroides was observed during early fermentation (pH 5.64-4.27 and acidity 0.48-0.89%), and Lactobacillus sakei become dominant later in fermentation (pH <or=4.15 and acidity >or=0.98%). The efficiency of the multiplex PCR ranged from 86.5% at day 0 (pH 6.17 and acidity 0.24%) to 100% at day 96 (pH 4.16 and acidity 1.14). This multiplex PCR assay will facilitate study of the microbial ecosystem of kimchi and its impact on kimchi fermentation.

Biodegradation of Chlorpyrifos by Lactic Acid Bacteria during Kimchi Fermentation

We examined the role of microorganisms in the degradation of the organophosphorus (OP) insecticide chlorpyrifos (CP) during kimchi fermentation. During the fermentation of kimchi, 30 mg L(-1) of CP was added and its stability assayed during fermentation. CP was degraded rapidly until day 3 (83.3%) and degraded completely by day 9. Four CP-degrading lactic acid bacteria (LAB) were isolated from kimchi fermentation in the presence of 200 mg L(-1) CP and were identified as Leuconostoc mesenteroides WCP907, Lactobacillus brevis WCP902, Lactobacillus plantarum WCP931, and Lactobacillus sakei WCP904. CP could be utilized by these four strains as the sole source of carbon and phosphorus. Coumaphos (CM), diazinon (DZ), parathion (PT), and methylparathion (MPT) were also degraded by WCP907, WCP902, WCP931, and WCP904 when provided as sole sources of carbon and phosphorus.

Organophosphorus hydrolase (OpdB) of Lactobacillus brevis WCP902 from kimchi is able to degrade organophosphorus pesticides.

Lactobacillus brevis WCP902 that is capable of biodegrading chlorpyrifos was isolated from kimchi. The opdB gene cloned from this strain revealed 825 bp, encoding 274 aa, and an enzyme molecular weight of about 27 kDa. OpdB contains the same Gly-X-Ser-X-Gly motif found in most bacterial and eukaryotic esterase, lipase, and serine hydrolases, yet it is a novel member of the GDSVG family of esterolytic enzymes. Its conserved serine residue, Ser82, is significantly involved with enzyme activity that may have application for removing some pesticides. Optimum organophosphorus hydrolase (OpdB) activity appeared at pH 6.0 and 35 degrees C and during degradation of chlorpyrifos, coumaphos, diazinon, methylparathion, and parathion.

Metagenomic characterization of oyster shell dump reveals predominance of Firmicutes bacteria

Metagenomic analyses were conducted to evaluate the biodiversity of oyster shell bacteria, under storage conditions, on the basis of 16s rDNA sequences. Temperature was recorded during a one year storage period, and the highest temperature (about 60°C) was observed after five months of storage. Bacterial diversity was greatest in the initial stage sample, with 33 different phylotypes classified under seven phyla (Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia and unclassified bacteria), with 42.22% of phylotypes belonging to Proteobacteria. The lowest diversity was found in the high temperature (fermentation) stage sample, with 10 different phylotypes belonging to Firmicutes (78.57%) and Bacteroidetes. In the final stage sample, bacteria were found belonging to Proteobacteria, Bacteroidetes, and Firmicutes, and some were unclassified bacteria. Of the bacteria constituting the final stage metagenome, 69.70% belonged to Firmicutes. Our results show that bacteria belonging to phylum Firmicutes were predominant during fermentation, and during the final stages of oyster shell storage, which suggests that these bacteria supposed to be the key players for oyster shell biodegradation.

Use of Bottom Ash of Waste Coal as an Effective Microbial Carrier

An experiment was done to determine the efficacy of waste bottom ash as an effective microbial carrier. Bottom ash found to be a suitable microbial carrier. The average of viable cells of Paenibacillus polymyxa GS01 (as a test biocontrol agent) in bottom ash samples was about 108 cfu/10±2 mg. The surface of bottom ash coated with 5% PVA w/v was most effective for improvement of cell viability. TSB medium containing 50 mg/L of MnSO4·H2O was the best for spore production of P. polymyxa GS01. Thus waste bottom ash coating with 5% PVA is likely to be suitable for use as a microbial carrier.