scholarly journals Characterization of the Psychrotrophic Lactic Acid Bacterium Leuconostoc gelidum subsp. aenigmaticum LS4 Isolated from Kimchi Based on Comparative Analyses of Its Genomic and Phenotypic Properties

Foods ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1899
Author(s):  
So Yeong Mun ◽  
Ye Jin Seo ◽  
Hae Choon Chang
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Low Temperatures ◽  
Starter Culture ◽  
Phenotypic Properties ◽  
Circular Chromosome ◽  
Maximum Cell ◽  
Leuconostoc Gelidum ◽  
Strong Antimicrobial Activity

With the aim of developing a new food starter culture, twenty-three psychrotrophic lactic acid bacteria (LAB) were isolated from 16 kimchi samples. One strain, Leuconostoc gelidum subsp. aenigmaticum LS4, which had typical psychrotrophic characteristics, was selected, and its phenotypic and genomic properties as a starter culture were investigated. The complete genome of L. aenigmaticum LS4 consisted of one circular chromosome (1,988,425 bp) and two plasmids (19,308 bp and 11,283 bp), with a guanine–cytosine content of 36.8%. L. aenigmaticum LS4 could grow at 5 °C but not at 37 °C, and maximum cell growth was obtained at 15~25 °C. L. aenigmaticum LS4 did not show any harmful characteristics such as hemolysis, undesirable enzyme activities, biogenic amine production, or antibiotic resistance. L. aenigmaticum LS4 was investigated for its suitability for technological processes (pH, temperature and NaCl treatment). L. aenigmaticum LS4 exhibited strong antimicrobial activity caused by the production of organic acids and bacteriocin, and it produced an exopolysaccharide composed of glucose with a molecular weight of 3.7 × 106 Da. Furthermore, L. aenigmaticum LS4 improved the organoleptic qualities of kimchi juice. Our results indicate that L. aenigmaticum LS4 could be used as a functional starter culture for food (vegetable or fruit) fermentation at low temperatures.

Study on the Preparation and Characterization of Carboxyl Terminated Poly(L-Lactic Acid) (PLLA) Prepolymers

2017 ◽  
Vol 872 ◽  
pp. 165-170
Author(s):  
Shi Chao Lu ◽  
Yang Chuan Ke ◽  
Qian Zhou ◽  
Zhao Rui Meng ◽  
Guo Liang Zhang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Average Molecular Weight ◽  
Polymerization Temperature ◽  
Capping Agent ◽  
Molar Amount ◽  
Optimum Reaction ◽  
Catalyst Content ◽  
End Capping

The carboxyl terminated poly (L-lactic acid) (PLLA) prepolymers were prepared via polycondensation of L-lactic acid and 1,6-adipic acid (end capping agent) under the catalyst of stannous octoate. The effects of synthetic condition, such as reaction temperature, amount of catalyst, content of the end capping agent, etc, on the molecular weight of PLLA were discussed. Fourier transform infrared and 1H nuclear magnetic resonance were used to characterize the PLLA prepolymers. The results indicated that the polycondensation was performed under an optimum reaction condition as following: the amount of the catalyst was 500 ppm based on the mass of lactic acid, the amount of the end capping agent was 1% (the molar amount of the lactic acid), and the polymerization temperature was 170 °C. The viscosity-average molecular weight of the product reached 2.826×104 at this polymerization temperature and the yield was 73.34%.

Studies on the manufacture of sweet cream starter butter: II. Effect of variation in proportion of starter added to cream

1960 ◽  
Vol 27 (1) ◽  
pp. 91-102 ◽  
Author(s):  
F. H. McDowall ◽  
J. A. Singleton ◽  
B. S. Le Heron
Keyword(s):  
Lactic Acid ◽  
Low Temperatures ◽  
Starter Culture ◽  
Skim Milk ◽  
Ph Values ◽  
Commercial Scale ◽  
Increase With Increase ◽  
Keeping Quality ◽  
Higher Temperature

SummaryProduction of diacetyl and acetoin by starters in cold skim-milk and cream was shown to increase with increase in the proportion of starter culture added, with some limitations at the higher rates of starter addition.With Streptococcus diacetilactis starter in skim-milk at 50°F the relation between proportion of starter added and production of diacetyl was linear up to addition at the 4% level, whereas at 43°F it was approximately linear up to the 10% level. At both 50 and 43°F the relation between the proportion of starter added and the production of acetoin was linear up to the 10% level.With Camb starter in skim-milk at both 50 and 43°F there were regular increases in production of diacetyl up to the 4% level of addition, but only minor changes thereafter with increase in the proportion of starter added up to 10%. At both temperatures the maximum production of acetoin was reached with the 7% rate of addition.Production of diacetyl and acetoin in skim-milk was greater at 50°F than at 43°F with both starters for all proportions up to 10%, and it was greater for Str. diacetilactis than for the mixed cultures.Except at the higher rates of addition of starter and at the higher temperature there were no concomitant increases in the acidity of the milk or lowering of the pH values. It appears that at low temperatures production of diacetyl by starters in sweet milk and cream proceeds independently of production of lactic acid.Similar results were obtained in a series of experimental buttermaking trials and some small commercial-scale trials, in which varying proportions of starter were added to creams after pasteurizing and before holding overnight for churning. With the cream-holding temperatures used, mainly 40–50°F, the pH values of the butters were not appreciably lowered by the starter additions to the cream. At all the rates of addition there were with Str. diacetilactis starter higher contents of diacetyl in the butter than with Camb starter. There was no indication of any relationship between the proportion of starter added and the keeping quality of the butter.

Preparation and Characterization of Poly(lactic acid) with Different Molecular Weights by Thermal Hydrolysis

2013 ◽  
Vol 440 ◽  
pp. 19-24 ◽  
Author(s):  
Jun Yan Yao ◽  
Loogn Tak Lim ◽  
Yu Jie Li
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Hydroxyl Group ◽  
Poly Lactic Acid ◽  
Thermal Hydrolysis ◽  
Molecular Weights ◽  
Hydrolytic Reaction ◽  
Structures And Properties ◽  
Ft Ir

A feasible and effective method of thermal hydrolysis to prepare poly (lactic acid) (PLA) oligomers with different controlled molecular weight from PLA is presented in this paper. The thermal hydrolytic reaction was carried out by immerging PLA resin pellets in boiling distilled water for a certain period of time. Ester groups in PLA chains are hydrolytically degraded in the presence of water and thermal, so PLA oligomers with different molecular weight were prepared. The structures and properties of PLA oligomers were characterized by FT-IR, GPC, DSC, etc. The results showed that thermal hydrolytic reaction could effectively reduce the molecular weight of PLA, which declines with the increase of the thermal hydrolytic reaction time. Meanwhile, the content of terminal hydroxyl group, glass transition temperature, melting point of PLA oligomers prepared from thermal hydrolytic reactions exhibit gradual changes with the extension of the thermal hydrolytic time.

scholarly journals Purification and Characterization of an Extracellular Poly(l-Lactic Acid) Depolymerase from a Soil Isolate,Amycolatopsis sp. Strain K104-1

2001 ◽  
Vol 67 (1) ◽  
pp. 345-353 ◽  
Author(s):  
Kohei Nakamura ◽  
Toshio Tomita ◽  
Naoki Abe ◽  
Yoshiyuki Kamio
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Collagen Type I ◽  
Type I ◽  
Chloromethyl Ketone ◽  
Diisopropyl Fluorophosphate ◽  
Soil Isolate ◽  
Solid Film ◽  
Subtilisin Inhibitor

ABSTRACT Poly(l-lactic acid) (PLA)-degradingAmycolatopsis sp. strains K104-1 and K104-2 were isolated by screening 300 soil samples for the ability to form clear zones on the PLA-emulsified mineral agar plates. Both of the strains assimilated >90% of emulsified 0.1% (wt/vol) PLA within 8 days under aerobic conditions. A novel PLA depolymerase with a molecular weight of 24,000 was purified to homogeneity from the culture supernatant of strain K104-1. The purified enzyme degraded high-molecular-weight PLA in emulsion and in solid film, ultimately forming lactic acid. The optimum pH for the enzyme activity was 9.5, and the optimum temperature was 55 to 60°C. The PLA depolymerase also degraded casein and fibrin but did not hydrolyze collagen type I, triolein, tributyrin, poly(β-hydroxybutyrate), or poly(ε-caprolactone). The PLA-degrading and caseinolytic activities of the enzyme were inhibited by diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride but were not significantly affected by soybean trypsin inhibitor,N-tosyl-l-lysyl chloromethyl ketone,N-tosyl-l-phenylalanyl chloromethyl ketone, and Streptomyces subtilisin inhibitor. Thus, Amycolatopsis sp. strain K104-1 excretes the unique PLA-degrading and fibrinolytic serine enzyme, utilizing extracellular polylactide as a sole carbon source.

scholarly journals Phenotypic characterization and ecological succession of microorganisms during the fermentation of Cassava and Maize

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Michael Ukwuru ◽  
Ome Kalu Achi ◽  
Uchechi Nnambuihe Ekwenye
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Large Population ◽  
Starter Culture ◽  
Morphological Characteristics ◽  
Ecological Succession ◽  
Phenotypic Characterization ◽  
Fermented Foods ◽  
Phenotypic Characteristics

Fermented foods are consumed by a very large population in Africa but the products have many drawbacks ranging from shelf life instability to contamination and toxicity. These foods therefore require an upgrade through improved fermentation processes. This work determined the phenotypic characteristics of the fermenting microorganisms and microbial ecological succession during fermentation of cassava and maize to determine the predominant fermenting microorganisms. Cassava roots and maize grains were fermented using the traditional method of processing them into fufu and ogi for 72 h and 48 h respectively. Samples were drawn every 12 h for analysis. Enumeration and characterization of lactic acid bacteria were carried out on MRS medium with subsequent microscopic examination, physiological, biochemical reaction tests and API 50 CH gallery. Yeast isolates were identified by their morphological characteristics. Thirteen lactic acid bacteria were isolated from the fermenting cassava and 6 from the fermenting maize. The Isolates were Gram positive and catalase negative. Lactobacillus plantarum, L. fermentum and L. pentusus predominated in both fermentations while Candida tropicalis, C. krusei and Saccharomyces cerevisae also predominated in both fermentations. Candida inconspicuo was found only in cassava fermentation. The results of this work revealed the microbial ecology of fermented cassava and maize which is a prerequisite to the understanding needed to develop a multifunctional starter culture for these fermentations for their upgrade. Keywords: Cassava, Maize, Fermentation, lactic acid bacteria, Yeasts.

Characterization of poly(lactic acid)s with reduced molecular weight fabricated through an autoclave process

2017 ◽  
Vol 60 ◽  
pp. 132-139 ◽  
Author(s):  
Kartik Behera ◽  
Yen-Hsiang Chang ◽  
Fang-Chyou Chiu ◽  
Jen-Chang Yang
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Poly Lactic Acid ◽  
Autoclave Process

scholarly journals Characterization of Weissella koreensis SK Isolated from Kimchi Fermented at Low Temperature (around 0 °C) Based on Complete Genome Sequence and Corresponding Phenotype

2020 ◽  
Vol 8 (8) ◽  
pp. 1147 ◽  
Author(s):  
So Yeong Mun ◽  
Hae Choon Chang
Keyword(s):  
Low Temperature ◽  
Complete Genome ◽  
Starter Culture ◽  
Arginine Deiminase ◽  
Circular Chromosome ◽  
Alternative Carbon Source ◽  
High Production ◽  
Energy Supplementation ◽  
Potential Use

This study identified lactic acid bacteria (LAB) that play a major role in kimchi fermented at low temperature, and investigated the safety and functionality of the LAB via biologic and genomic analyses for its potential use as a starter culture or probiotic. Fifty LAB were isolated from 45 kimchi samples fermented at −1.5~0 °C for 2~3 months. Weissella koreensis strains were determined as the dominant LAB in all kimchi samples. One strain, W. koreensis SK, was selected and its phenotypic and genomic features characterized. The complete genome of W. koreensis SK contains one circular chromosome and plasmid. W. koreensis SK grew well under mesophilic and psychrophilic conditions. W. koreensis SK was found to ferment several carbohydrates and utilize an alternative carbon source, the amino acid arginine, to obtain energy. Supplementation with arginine improved cell growth and resulted in high production of ornithine. The arginine deiminase pathway of W. koreensis SK was encoded in a cluster of four genes (arcA-arcB-arcD-arcC). No virulence traits were identified in the genomic and phenotypic analyses. The results indicate that W. koreensis SK may be a promising starter culture for fermented vegetables or fruits at low temperature as well as a probiotic candidate.

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