Genetic improvement of technological characteristics of starters for fermented milk products

Hovhannisyan, Hrachya; Barseghyan, A. A.; Grigoryan, N. G.; Topchyan, A. V.

doi:10.1134/s0003683810040058

Cited by 5 publications

(5 citation statements)

References 25 publications

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“…In order to study UV mutagenicity, rifampicin and streptomycin were used as selective agents for these experiments because of relatively low frequency of their spontaneous resistance mutations [8,14]. The mutation rates were derived after plating UV irradiated cultures LAPTg medium with antibiotic.…”

Section: Resultsmentioning

confidence: 99%

“…Also LAB high resistance was demonstrated by the increased recovery of live lactobacilli from irradiated food by comparison to staphylococcal and Salmonella species [19]. The intrinsic resistance of LAB to chemical mutagens such as N-Methyl-N′-nitro-N-nitrosoguanidine (NG) is also significantly higher than E. coli [8,14].…”

Section: Discussionmentioning

confidence: 99%

“…However, it is rarely used toward lactic acid bacteria [7]. The N-Methyl-N′-nitro-N-nitrosoguanidine (NTG) induced mutagenesis was used to increase of yields of streptomycin and rifampicin resistant mutant starters with improved technological and organoleptic characteristics in L. acidophilus [8]. The mechanism of UV induced mutagenesis of LAB is purely investigated.…”

Section: Introductionmentioning

confidence: 99%

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UV - Induced Mutagenesis in Lactic Acid Bacteria

Goodarzi¹

2016

IJGG

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Induced mutagenesis is widely used for selection of microorganisms producing biologically active substances and further improving of their activities. However, it is rarely used toward lactic acid bacteria (LAB) due to their genetic specificity. Determination of LABs sensitivity to UV light and evaluate the effectiveness of UV-induced mutagenesis by positive selection of antibiotic resistant mutants. Bacterial cells grown in LAPTg and NB broth up to late log phase were harvested by centrifugation and resuspended in phosphate buffer (pH 6.8) and irradiated by UV (15 w paired lamps) at distance of 30 cm and plated on LAPTg and NB agars with and without antibiotics for survivors count and positive selection of Rif and Str colonies. It was revealed that lactic acid bacteria were 1 to 2 log more resistant to UV in compression with E. coli. At dose 40 sec the difference in survival between L. lactis and E. coli was not so significant. The yield of rifampicin and streptomycin resistant mutants of LABs vary depending of UV exposure. The maximum yield about 2-3 log of both types of resistant mutants in lactobacilli and lactococcus were observed at dose 20 sec (0.1% survival). LAB possesses intrinsic resistance to UV irradiation 1-2 log higher than E. coli. The maximum yield of UV induced Rif and Str mutants in all LABs occurs at survival about 0.1%. Thus UV rays as an effective mutagen can be used in selection of dairy starters with improved technological and probiotics characteristic.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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UV - Induced Mutagenesis in Lactic Acid Bacteria

Goodarzi¹

2016

IJGG

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“…The culture of L. delbrueckii was subjected to NG mutagenesis with concentration of 300 μg/ml for 30 min as described earlier (Hovhannisyan et al 2010). Appropriate dilution of NG treated cultures was plated on LAPTg agar with (100µg/ml) and without rifampicin and incubated for 48 hours at 37 °C.…”

Section: Ng Induced Mutagenesis and Isolation Of Rifampicin Resistant...mentioning

confidence: 99%

Enhancement of Hydrogen Peroxide Production by RNA Polymerase rif Mutations of Lactobacillus delbrueckii subsp. lactis MDC 9617

Hovhannisyan

Gaboyan

Barseghyan

et al. 2022

Preprint

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It was found out that among rifampicin resistant mutants (Rif) of Lactobacillus delbrueckii subsp. lactis MDC 9617 the frequency of occurrence of active hydrogen peroxide producers is about five times higher than in Rif + strain. Aerobically growing Rif mutants show relatively higher kinetics of H 2 O 2 production and earlier entry into the stationary phase due to auto-inhibition caused by inhibitory concentrations of H 2 O 2 . As a result, they synthesize about the same amount of H 2 O 2 but with a smaller biomass. The concentration of H 2 O 2 , which causes auto-inhibition of aerobically growing cultures is approximately 2 times lower than the MIC of exogenous H 2 O 2 for anaerobically growing cultures. The higher sensitivity of aerobically growing cultures is rather due to the existing intracellular H 2 O 2 , which together with extracellular H 2 O 2 causes an additive/cumulative effect. Lack of auto-inhibition at 5 °C allows the mutants to accumulate 50-70% more peroxide than the parental strain. Reduction of the food-borne pathogen Escherichia coli O157:H7 by selected active Rif-4 mutant during co-cultivation in LAPTg at 5 °C was significantly higher than that of the parental strain. Due to high (~40%) co-aggregation ability of LAB with E. coli , the death of the pathogen detected at an early stage of co-cultivation in the absence of inhibitory concentrations of H 2 O 2 , may occur by direct release of H 2 O 2 onto the target cell. The ability of Rif mutants to produce higher amounts of H 2 O 2 with a smaller biomass enable them to extend the shelf-life of refrigerated food without risk of altering sensory characteristics of the latter.

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“…However, further increase in the activity of CA producing strains is connected with certain diffi culties due to the complicated regulation of its biosyn thesis accomplished with participation of more than 19 genes [7]. A slight increase in the activity of other EPS producers was achieved by obtaining gramicidin resistant mutations affecting the cell membrane struc tures responsible for polycondensation reaction of activated nucleosugars [15][16][17]. 1 The article was translated by the authors.…”

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confidence: 99%