• International Journal of Advanced Culture Technology
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• v.3 no.2
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• pp.100-109
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• 2015

Environmental problems from petroleum-based plastic wastes have been rapidly increasing in recent years. The alternative solution is focus on the development of environmental friendly plastic derived from renewable resource. Poly(lactic acid) (PLA) is a biodegradable polymer synthesized from biomass having potential to replace the petroleum-based non-degradable polymers utilizations. PLA can be synthesized by two methods: (1) ring-opening of lactide intermediate and (2) direct polycondensation of lactic acid processes. The latter process has advantages on high yields and high purity of polymer products, materials handling and ease of process treatments. The polymerization process of PLA synthesis has been widely studied in a laboratory scale. However, the mass scale production using direct polycondensation of lactic acid has not been reported. We have investigated the kinetics and scale-up process of direct polycondensation method to produce PLA in a pilot scale. The order of reaction is 2 and activation energy of lactic acid to lactic acid oligomers is 61.58 kJ/mol. The pre-polymer was further polymerized in a solid state polymerization (SSP) process. The synthesized PLA from both the laboratory and pilot scales show the comparable properties such as melting temperature and molecular weight. The appearance of synthesized PLA is yellow-white solid powder.

• Korean Journal of Food Science and Technology
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• v.28 no.1
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• pp.117-121
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• 1996

In order to find the reason for souring of Hansan sogokju (Korean traditional rice wine), microbial distribution, pH change and organic acids were analysed. Besides 161 mM of lactic acid as a major organic acid, small amount of acetic acid, malic acid, propionic acid were found in sogokju. Four different microbial strains were identified from the sogokju. These are two strains of Lactobacillus spp., Bacillus sp. and yeast. The pH of sogokju was changed from 4.01 to 3.29 during 18 days storage at $30^{\circ}C$. Amount of total acidity increased from 9 to 34.86 at the same condition. Notable change in the soured sogokju was an increase of the lactic acid (from 161 mM to 192 mM). So, we could assume that it was soured by an additional production of lactic acid by lactic acid bacteria during storage. The shelf life of sogokju was 41 days below $15^{\circ}C$ degree because this temperature was hard condition for the growth of Lactobacillus spp., causative bacteria responsible for additional lactic acid production.

• Journal of Microbiology
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• v.41 no.3
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• pp.175-182
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• 2003

Production of ribosomally synthesized antimicrobial peptides usually referred to as bacteriocins is an inducible trait in several gram positive bacteria, particularly in those belonging to the group of lactic acid bacteria. In many of these organisms, production of bacteriocins is inducible and induction requires secretion and extracellular accumulation of peptides that act as chemical messengers and trigger bacteriocin production. These inducer peptides are often referred to as autoinducers and are believed to permit a quorum sensing-based regulation of bacteriocin production. Notably, the peptides acting as autoinducers are dedicated peptides with or without antimicrobial activity or the bacteriocins themselves. The autoinducer-dependent induction of bacteriocin production requires histidine protein kinases and response regulator proteins of two-component signal transduction systems. The current working model for the regulation of class II bacteriocin production in lactic acid bacteria and the most relevant direct and indirect pieces of evidence supporting the model are discussed in this minireview.

• Preventive Nutrition and Food Science
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• v.9 no.3
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• pp.206-212
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• 2004

Prickly pear extract (PPE) was fermented by Lactobacillus rhamnosus LS at 3$0^{\circ}C$ for 2 days. To improve the physicochemical properties of fermented PPE, it was fortified with food polysaccharides (0.2 %) or seaweed calcium before lactic acid fermentation. The viable cell counts, flow behavior, titratable acidity and color stability of fermented PPE were evaluated during 4 weeks of cold storage. Addition of xanthan gum or glucomannan increased the apparent viscosity and acid production, viable cell counts and red color of PPE were also well maintained during the cold storage. However, fermenting PPE with gellan gum resulted in a decrease in relative absorbance, indicating lower color stability. In particular, PPE fortified with carrageenan or alginic acid showed reduced acid production and lower viable cell counts. Addition of seaweed calcium at a 0.1 % level had positive effects on color stability, and helped maintain viable cell counts of 4.1 ${\times}$ 10$^{9}$ CFU/mL. This study demonstrated that xanthan gum could be used as a good thickening agent and stabilizer for retaining viable cell counts and red color during the cold storage in PPE fermented by lactic acid bacteria.

• Journal of Food Hygiene and Safety
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• v.37 no.1
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• pp.21-28
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• 2022

In this study, a new lactic acid bacterium (LAB) that could produce gamma-aminobutyric acid (GABA) was isolated from Oenanthe javanica (water celery) and identified as an Enteroccoccus casseliflavus strain. Until recently, there have been many studies on the gamma-aminobutyric acid producing lactic acid bacterium, as well as on some lactic acid bacterium in Enteroococcs genus, but none on the species E. casseliflavus. Therefore, in the purpose of finding the optimal conditions for GABA production of E. casseliflavus PL05, the effects of several conditions including the type of mediums, growth temperatures, initial pH, growth time, L-mono sodium glutamate (MSG) concentration, and carbon source were tested. The study revealed that the PL05 strain grew better in the Brain Heart Infusion (BHI) medium than in the Man, Rogosa, and Sharpe (MRS) or Tryptic Soy Broth (TSB) medium. Also, similar results were obtained with GABA production conditions. As a result of analysis on the GABA production yield by concentration of MSG, a GABA substrate, the highest production was found at 7% of MSG concentration. However, since similar level of production was found at 5%, it is considered to be more efficient to use 5% MSG concentration. The analysis on the growth and GABA production yield by carbon sources showed the highest results when maltose was used. From the final test under the optimal conditions found, 140.06±0.71 mM of GABA was produced over 24 hours with the conversion rate of 78.95%. Lastly, from the sensitivity analysis on the 10 different antibiotics, including vancomycin, it was found that there were not confirmed cases of resistance.

• Food Science of Animal Resources
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• v.35 no.4
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• pp.473-478
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• 2015

The aim of this study was to screen and In vitro characterize the properties of bacteriocin produced by lactic acid bacteria isolated from Vietnamese fermented pork (Nem chua). One hundred and fifty LAB were isolated from ten samples of Nem chua and screened for bacteriocin-producing lactic acid bacteria. Antimicrobial activity of bacteriocin was carried out by spot on lawn method against both gram positive and gram negative bacteria. One isolate, assigned as KL-1, produced bacteriocin and showed inhibitory activity against Lactobacillus sakei, Leuconostoc mesenteroides and Enterococcus faecalis. To characterize the bacteriocin-producing strain, optimum temperature, incubation period for maximum bacteriocin production and identification of bacteriocin-producing strain were determined. It was found that the optimum cultivation temperature of the strain to produce the maximum bacteriocin activity (12,800 AU/mL) was obtained at 30℃. Meanwhile, bacteriocin production at 6,400 AU/mL was found when culturing the strain at 37℃ and 42℃. The isolate KL-1 was identified as L. plantarum. Antimicrobial activity of cell-free supernatant was completely inhibited by proteolytic enzyme of trypsin, alpha-chymotrypsin and proteinase K. Bacteriocin activity was stable at high temperature up to 100℃ for 10 min and at 4℃ storage for 2 d. However, the longer heating at 100℃ and 4℃ storage, its activity was reduced.

• Current Research on Agriculture and Life Sciences
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• v.7
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• pp.23-32
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• 1989

This experiment was performed to investigate the growth and acid production of lactic acid bacteria in soy yoghurts prepared from soybeans produced using various nitrogen sources and the ability of the bacteria to utilize the available carbohydrates in the medium. Various soybeans did not show significant difference in the growth and acid production of lactic acid bacteria, soybean D with newly developed complex fertilizer being the best. The acid production in soy milk by L. acidophilus was better than those in defatted soy milk and in isolated soy protein, that in isolated soy milk being significantly poor. Of lactic acid bacteria tested, L bulgaricus and L. acidophilus exhibited more population and acid production in soy yoghurts. The population and acid production of lactic acid bacteria was increased by the addition of various carbohydrates, and significantly by glucose and yeast extract.

• Korean Journal of Food Science and Technology
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• v.21 no.3
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• pp.379-386
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• 1989

The soy milk prepared from soy protein concentrate was treated with microbial protease or papain. Growth and acid production by Lactobacillus acidophilus in soy milk containing partially hydrolyzed proteins were investigated. Sensory evaluation of yogurt beverage prepared from protease treated soy milk was also performed. Protease treatment of soy milk enhanced acid production by lactic acid bacteria, particularly in case of microbial pretense and simultaneous treatment by two types of protease showed synergistic effect. pH and number of viable cells were not affected markedly by pretense treatment. Microbial pretense treatment up to 15 minutes or papain treatment up to 45 minutes enhanced acid production, but further treatment up to three hours did not affect the acidity markedly. rho sensory evaluation showed that overall acceptability and taste of soy yogurt beverage were slightly improved when soy milk was treated with microbial pretense of 0.2% or papain of 0.2%. The amount of non-protein nitrogen considerably increased by pretense treatment of 15 minutes and it increased gradually by further treatment up to three hours.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.6
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• pp.783-791
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• 2019

Objective: This study was to evaluate the fermentation dynamics, structural and nonstructural carbohydrate composition and in vitro gas production of rice straw ensiled with lactic acid bacteria and molasses. Methods: Fresh rice straw was ensiled in 1-L laboratory silos with no additive control (C), Lactobacillus plantarum (L), molasses (M) and molasses+Lactobacillus plantarum (ML) for 6, 15, 30, and 60 days. After storage, the silages were subjected to microbial and chemical analyses as well as the further in vitro fermentation trial. Results: All additives increased lactic acid concentration, and reduced pH, dry matter (DM) loss and structural carbohydrate content relative to the control (p<0.05). The highest organic acid and residual sugar contents and lignocellulose reduction were observed in ML silage. L silage had the highest V-score with 88.10 followed by ML silage. L and ML silage improved in vitro DM digestibility as compared with other treatments, while in vitro neutral detergent fibre degradability (IVNDFD) was increased in M and ML silage (p<0.05). M silage significantly (p<0.05) increased propionic acid (PA) content and decreased butyric acid content and acetic acid/PA as well as 72-h cumulative gas production. Conclusion: The application of ML was effective for improving both the fermentation quality and in vitro digestibility of rice straw silage. Inclusion with molasses to rice straw could reduce in vitro ruminal gas production.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.2
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• pp.95-102
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• 2023

Despite the easing of social distancing, demand for non-face-to-face services continues to rise. Recently, the EU is pursuing a comprehensive plastic use reduction by expanding the scope of plastic use regulations for packaging plastics according to the New Cyclical Economy Action Plan(NCEAP). In response to this trend, the packaging industry is moving away from conventional non-degradable/petroleum-based plastics and conducting research on packaging materials using biodegradable plastics such as PLA(Poly Lactic Acid), PBAT(Poly Butylene Adipate-co-butylene Terephthalate). On the other hand, ginkgo leaves occur in large quantities in Korea and act as a cause of slip accidents and flooding. In this study, a method to utilize ginkgo biloba leaf as a new alternative biomass resource was proposed by producing lactic acid through pretreatment, enzymatic saccharification, and fermentation processes. For the efficiency of lactic acid production, a comparative analysis of lignin content from before and after browning was performed. In addition, the degree of glucan extraction was evaluated by applying a pretreatment method using three catalysts: hot water, sulfuric acid, and sodium hydroxide. It is difficult to expect high production of lactic acid with single process. Therefore, an integrated process operation using both the pretreated hydrolyzate and the residual solid enzymatic saccharification solution must necessarily be applied.