Biomedical subjects

R P Ross

Publications and source records attributed to R P Ross.

At least 19 recordsLinked to original sources

PubMed2003

Conjugated linoleic acid biosynthesis by human-derived Bifidobacterium species.

AIMS: To assess strains of Lactobacillus, Lactococcus, Pediococcus and Bifidobacterium for their ability to produce the health-promoting fatty acid conjugated linoleic acid (CLA) from free linoleic acid. METHODS AND RESULTS: In this study, strains of Lactobacillus, Lactococcus, Pediococcus and Bifidobacterium were grown in medium containing free linoleic acid. Growth of the bacteria in linoleic acid and conversion of the linoleic acid to CLA was assessed. Of the bacteria assessed, nine strains of Bifidobacterium produced the c9, t11 CLA isomer from free linoleic acid. The t9, t11 CLA isomer was also produced by some strains, but at much lower concentrations. CONCLUSIONS: The production of CLA by bifidobacteria exhibited considerable interspecies variation. Bifidobacterium breve and B. dentium were the most efficient CLA producers among the range of strains tested, with B. breve converting up to 65% linoleic acid to c9, t11 CLA when grown in 0.55 mg ml(-1) linoleic acid. Strains also varied considerably with respect to their sensitivity to linoleic acid. SIGNIFICANCE AND IMPACT OF THE STUDY: The production of CLA by probiotic bifidobacteria offers a possible mechanism for some health-enhancing properties of bifidobacteria and provides novel opportunities for the development of functional foods.

Adult↗

PubMed2002

Use of lacticin 481 to facilitate delivery of the bacteriophage resistance plasmid, pCBG104 to cheese starters.

AIMS: Use of lacticin 481 to facilitate the conjugal transfer of the bacteriophage resistance plasmid pCBG104 to various starter cultures. METHODS AND RESULTS: A raw milk isolate of Lactococcus was found to harbour determinants for lacticin 481 production and immunity and phage resistance on a plasmid designated pCBG104. The lacticin 481 was successfully used to mobilize the phage resistance determinant to a variety of cheese starters enabling the formation of highly phage resistant starters. In addition, it facilitated the stacking of a number of phage resistance genes, namely a type I restriction modification system, a phage abortive infection system and a phage adsorption blocking system in a single Lactococcus strain without the use of recombinant techniques. The transconjugants were all shown to produce lacticin 481 and to contain the entire 481 operon. Subsequently one transconjugant was selected and successfully used for large-scale cheddar cheese manufacture. CONCLUSIONS: Lacticin 481 could be used as a food-grade selectable marker to facilitate the introduction of advantageous traits to starter cultures for industrial food fermentations. SIGNIFICANCE AND IMPACT OF THE STUDY: Food-grade selectable markers greatly facilitate the introduction of various advantageous traits to starter cultures for industrial food fermentation. Indeed self-cloning which is becoming increasingly important for strain improvement has a requirement for the identification and demonstration of the utility of tools such as lacticin 481.

Bacterial Proteins↗

PubMed2002

Lactococcus lactis DPC5598, a plasmid-free derivative of a commercial starter, provides a valuable alternative host for culture improvement studies.

AIMS: To generate a plasmid-free derivative of an extensively used industrial starter strain Lactococcus lactis DPC4268, which could be used as a backbone strain for starter improvement programmes. METHODS AND RESULTS: DPC4268 containing four large plasmids was subjected to high temperature plasmid curing resulting in derivatives, each with a different plasmid complement of one, two or three different plasmids in addition to a plasmid-free derivative. Industrially relevant phenotypes were assigned to each plasmid on the basis of detailed phenotypic and genetic analyses and these were (a) proteinase activity (Prt, 60 kb) (b) lactose fermentation (Lac, 55 kb) (c) bacteriophage adsorption inhibition (Ads, 44 kb) and (d) type I restriction/modification (R/M, 40 kb). The plasmid-free variant of DPC4268 was shown to be transformable at frequencies comparable to the common laboratory strain L. lactis MG1614. Furthermore its genome was demonstrated to be significantly different from the laboratory strains L. lactis MG1614 and the recently sequenced L. lactis IL1403 genomes by pulsed-field gel electrophoresis. CONCLUSIONS: This study produced an easily transformable plasmid-free derivative which was genomically different from both MG1614 and IL1403. In addition, important plasmid-borne industrial traits, including two phage-resistance mechanisms, were identified in DPC4268. SIGNIFICANCE AND IMPACT OF THE STUDY: L. DPC4268 is a vitally important commercial strain used in the manufacture of Cheddar cheese. The generation of a plasmid-free derivative may provide an important backbone strain as a basis for future strain improvement purposes.

Bacteriophages↗

PubMed2002

Improved survival of Lactobacillus paracasei NFBC 338 in spray-dried powders containing gum acacia.

AIMS: To assess the protective effect of gum acacia (GA) on the performance of Lactobacillus paracasei NFBC 338 during spray-drying, subsequent storage and exposure of the culture to porcine gastric juice. METHODS AND RESULTS: For these studies, Lact. paracasei NFBC 338 was grown in a mixture of reconstituted skim milk (10% w/v) and GA (10% w/v) to mid log phase and spray-dried at outlet temperatures between 95 and 105 degrees C. On spray drying at the higher air outlet temperature of 100-105 degrees C, the GA-treated culture displayed 10-fold greater survival than control cells. Probiotic lactobacilli in GA-containing powders also survived dramatically better than untreated cultures during storage at 4-30 degrees C for 4 weeks. A 20-fold better survival of the probiotic culture in GA-containing powders was obtained during storage at 4 degrees C while, at 15 and 30 degrees C, greater than 1000-fold higher survival was obtained. Furthermore, the viability of probiotic lactobacilli in GA-containing powders was 100-fold higher when exposed to porcine gastric juice over 120 min compared with the control spray-dried culture. CONCLUSIONS: The data indicate that GA has applications in the protection of probiotic cultures during drying, storage and gastric transit. SIGNIFICANCE AND IMPACT OF THE STUDY: Gum acacia treatment for the manufacture of probiotic-containing powders should result in more efficient probiotic delivery to the host gastrointestinal tract.

Animals↗

PubMed2002

Genomic diversity within the genus Pediococcus as revealed by randomly amplified polymorphic DNA PCR and pulsed-field gel electrophoresis.

The genomic diversity of 33 previously assigned strains from six species within the genus Pediococcus was assessed by randomly amplified polymorphic DNA (RAPD) PCR and pulsed-field-gel electrophoresis (PFGE). The RAPD PCR patterns produced by two separate random primers, termed P1 (ACGCGCCCT) and P2 (ATGTAACGCC), were compared by the Pearson correlation coefficient and the unweighted pair group method with arithmetic averages clustering algorithm. Pattern variations between repeat samples set a strain discrimination threshold of less than 70% similarity. P1 and P2 primers alone and in combination produced 14, 21, and 28 distinct patterns, respectively. When each strain was assigned with a type strain with which it shared the highest level of similarity, both primers grouped 17 of the 27 strains to their proposed species. PFGE following genomic digestion with the restriction enzymes ApaI, NotI, and AscI produced 30, 32, and 28 distinct macrorestriction patterns, respectively. Specific DNA fragments within the NotI and AscI macrorestriction patterns for each strain were observed that allowed 27 of the 33 strains to be assigned to their proposed species. For example, following digestion with AscI, all Pediococcus parvulus strains were characterized by two DNA fragments, one of approximately 220 kb and another between 700 and 800 kb. The exceptions correlated with those observed with both RAPD PCR primers and included three P. damnosus and two P. pentosaceus strains that grew at temperatures regarded as nonpermissive for their proposed species but not for those with which they grouped.

Animals↗

PubMed2002

Elevated enzyme release from lactococcal starter cultures on exposure to the lantibiotic lacticin 481, produced by Lactococcus lactis DPC5552.

A Lactococcus lactis subsp. lactis strain (DPC5552), which causes the lysis of other lactococcal cultures, was isolated during a screening of raw milk samples for bacteriocin producers. Purification of the bacteriocin produced revealed that production of the lantibiotic, lacticin 481, was associated with the bacteriolytic capability of the strain. However, unlike bacteriocin-induced lysis observed with bacteriocins such as lacticin 3147 and lactococcins A, B, and M (where the target strain is killed), the DPC5552 supernatant gave rise to a situation whereby the target strain continued to grow (albeit at a lower rate) with simultaneous release of the intracellular enzymes lactate dehydrogenase (LDH) and post-proline dipeptidyl aminopeptidase (Pep X). In parallel experiments, 32 AU/ml of the inhibitory activity from L. lactis DPC5552 resulted in a 10- and 6-fold-higher LDH release after 5 h than that with 32 AU/ml of either lacticin 3147 or lactococcin A, B, and M. Laboratory-scale Cheddar cheese-making trials also demonstrated that lacticin 481-producing cultures induced the release of elevated levels of LDH from the starter L. lactis HP, without severely compromising its acid-producing capabilities. These results indicate that lacticin 481-producing strains may provide improved adjuncts for delivering lactococcal intracellular enzymes into the cheese matrix and, thus, improve cheese quality and flavor.

Bacterial Proteins↗

PubMed2002

Lantibiotics produced by lactic acid bacteria: structure, function and applications.

Lantibiotics are a diverse group of heavily modified antimicrobial and/or signalling peptides produced by a wide range of bacteria, including a variety of lactic acid bacteria. Based on their diverse structures and mode of action, at least six separate lantibiotic subgroups can be suggested, but all subgroups are characterized by significant post-translational modifications, which include the formation of (beta-methyl)lanthionines, among other unusual alterations. These small peptides are produced, modified, exported, sensed and combated by a complex set of proteins encoded by (usually) co-ordinately regulated operons. In some instances, the production and immunity have been shown to be auto-regulated by the mature lantibiotic. Since their discovery, interest in lantibiotics has been fuelled by their obvious potential as food-grade antimicrobials to improve food safety and quality; a potential which, to date, has been realised only by the longest characterised molecule, nisin. In addition, these peptides are often mooted as alternatives to antibiotics for some biomedical applications. The purpose of this paper is to review recent developments in our understanding of lantibiotic structure, molecular genetics and applications for this unusual class of bacteriocins.

Amino Acid Sequence↗

PubMed2001

Pre-inoculation enrichment procedure enhances the performance of bacteriocinogenic Lactococcus lactis meat starter culture.

Sodium nitrite and sodium chloride may inhibit growth and bacteriocinogenesis of protective starter cultures. To reduce sensitivity of a lacticin 3147-producing starter culture to nitrite, prior to production of salami, Lactococcus lactis DPC 4275 was placed in a number of pre-inoculation treatments, containing (a) 1% glucose, (b) 2.5 ppm manganese (Mn), (c) 250 ppm magnesium (Mg), (d) 2.5 ppm manganese + 250 ppm magnesium (Mn + Mg), and held at ambient temperature for 30 min and 4 degrees C for 2 h. The growth, pH reduction, and bacteriocin production was monitored in beaker sausage over a period of 10 days at 28 degrees C, corresponding to typical salami production time, and compared to untreated starter culture. The effect of 1% tryptone and inoculum level on growth and bacteriocin production was also determined. Challenge tests were performed using Listeria innocua DPC 1770 and Staphylococcus aureus MMPR3 as target strains. All treatments gave a significantly higher (P < 0.05) initial starter level than the untreated starter. Beaker sausage inoculated with either low (10(7)) or high (10(9)) levels of starter culture, treated with Mn + Mg reached significantly (P < 0.05) higher levels by day 10 than other treatments. Trends indicate that Mn + Mg also gave best pH reduction in sausage containing the low-level starter culture, sausage and significantly lower (P < 0.05) values for sausage produced with higher inoculum. Bacteriocin production was also higher in starter culture treated with Mn, or glucose. Pre-treatment with Mg gave a 2-fold increase in bacteriocin, the addition of Mn augmenting this increase further. The incorporation of tryptone gave no additional effect. In beaker sausage, both L. innocua and S. aureus populations showed significant reductions (P < 0.05) in the presence of the bacteriocinogenic strain compared to a non-bacteriocinogenic control strain.

Antibiosis↗

PubMed2001

Regulation of immunity to the two-component lantibiotic, lacticin 3147, by the transcriptional repressor LtnR.

Lacticin 3147 is a membrane-active, two-component lantibiotic produced by Lactococcus lactis ssp. lactis DPC3147. In this study, the promoters of the lacticin 3147 gene cluster were mapped to the intergenic region between ltnR and ltnA1 (the genes encoding the regulatory protein LtnR and the first structural gene, LtnA1), and Northern analyses revealed that the biosynthetic and immunity genes are divergently transcribed in two operons, ltnA1A2M1TM2D and ltnRIFE respectively. Although the promoter controlling biosynthesis (Pbac) appears to be constitutive, characterization of a downstream beta-galactosidase (beta-gal) fusion beyond an intragenic stem-loop structure in ltnM1 confirmed that this putative transcriptional attenuator allows limited readthrough to the downstream biosynthetic genes, thus maintaining the correct stoichiometry between structural peptides and biosynthetic machinery. The promoter of the ltnRIFE operon (Pimm) was shown to be regulated by the transcriptional repressor LtnR. A mutant with a truncated ltnR gene exhibited a hyperimmune phenotype, whereas overexpression of ltnR resulted in cells with increased sensitivity to lacticin 3147. Gel mobility shift analysis indicated that LtnR binds to the Pimm promoter region, and fusion of this promoter to the beta-gal gene of pAK80 revealed that expression from Pimm is significantly reduced in the presence of LtnR. Thus, we have demonstrated that lacticin 3147 uses a regulatory mechanism not previously identified in lantibiotic systems.

Anti-Bacterial Agents↗

PubMed2001

Heterologous expression of lacticin 3147 in Enterococcus faecalis: comparison of biological activity with cytolysin.

Lacticin 3147 is a broad-spectrum, two-component, lanthionine-containing bacteriocin produced by Lactococcus lactis DPC3147 which has widespread food and biomedical applications as a natural antimicrobial. Other two-component lantibiotics described to date include cytolysin and staphylococcin C55. Interestingly, cytolysin, produced by Enterococcus faecalis, has an associated haemolytic activity. The objective of this study was to compare the biological activity of lacticin 3147 with cytolysin. The lacticin 3147-encoding determinants were heterologously expressed in Ent. faecalis FA2-2, a plasmid-free strain, to generate Ent. faecalis pOM02, thereby facilitating a direct comparison with Ent. faecalis FA2-2.pAD1, a cytolysin producer. Both heterologously expressed lacticin 3147 and cytolysin exhibited a broad spectrum of activity against bacterial targets. Furthermore, enterococci expressing active lacticin 3147 did not exhibit a haemolytic activity against equine blood cells. The results thus indicate that the lacticin 3147 biosynthetic machinery can be heterologously expressed in an enterococcal background resulting in the production of the bacteriocin with no detectable haemolytic activity.

Amino Acid Sequence↗

PubMed2001

Evaluation of a spray-dried lacticin 3147 powder for the control of Listeria monocytogenes and Bacillus cereus in a range of food systems.

AIMS: The potential of a powdered preparation of the bacteriocin, lacticin 3147, was investigated for the inhibition of Listeria monocytogenes and Bacillus cereus. METHODS AND RESULTS: A 10% solution of reconstituted demineralized whey powder was fermented with Lactococcus lactis DPC3147 for the generation of a lacticin 3147 containing powdered product. A 99.9% reduction in L. monocytogenes numbers occurred in the presence of the lacticin 3147 powder within 2 h in natural yogurt, and an 85% reduction was observed in cottage cheese within the same time frame. Counts of B. cereus were reduced by 80% in soup, in the presence of 1% (w/w) lacticin 3147 powder, within 3 h. CONCLUSIONS: A powdered preparation of lacticin 3147 was effective for the control of Listeria and Bacillus in natural yogurt, cottage cheese and soup. SIGNIFICANCE AND IMPACT OF THE STUDY: The bioactive lacticin 3147 powder may find broad applications for control of Gram-positive pathogens/spoilage bacteria in a range of foods.

Bacillus cereus↗

PubMed2001

The use of cadmium resistance on the phage-resistance plasmid pNP40 facilitates selection for its horizontal transfer to industrial dairy starter lactococci.

AIMS: To facilitate the horizontal transfer and selection of phage-resistance plasmids in industrial lactococci. METHODS AND RESULTS: Cadmium-resistance properties similar to those previously identified in Lactococcus were linked to the well-known phage-resistance plasmid pNP40. This finding was exploited to facilitate delivery of the plasmid to an industrial cheese starter Lactococcus lactis DPC4268. Additionally, 25 different cadmium-sensitive cheese starter lactococci were also identified as potential recipients for the phage-resistance plasmid pNP40, and also the plasmids pAH90/pAH82 which also encode cadmium resistance. All three plasmids were successfully conjugated to strain DPC4268. Cheddar cheese was manufactured in industry with the pNP40 phage-resistant transconjugant. SIGNIFICANCE AND IMPACT OF THE STUDY: Food-grade enhancement of phage resistance in industrial starter strains has been made simpler by the use of this selection, especially since the majority of potential recipient starter strains analysed were cadmium sensitive.

Bacteriophages↗

PubMed2001

Market potential for probiotics.

"Functional foods" as a marketing term was initiated in Japan in the late 1980s and is used to describe foods fortified with ingredients capable of producing health benefits. This concept is becoming increasingly popular with consumers because of a heightened awareness of the link between health, nutrition, and diet. Food manufacturers are enthusiastic about developing such products because the added ingredients give increased value to food. The global market for functional foods in the coming years is predicted to grow rapidly. Although Japan currently accounts for about one-half of this market, the fastest rate of growth is expected to be in the United States. Probiotic products represent a strong growth area within the functional foods group and intense research efforts are under way to develop dairy products into which probiotic organisms such as Lactobacillus and Bifidobacterium species are incorporated. Such probiotic foods may modulate gut microbial composition, thereby leading to improved gut health, for example, through improved tolerance to lactose in lactose-intolerant individuals or improved resistance to pathogenic bacteria. Large numbers of viable microorganisms are likely to be required in the food product, which should be consumed regularly to experience the health effect. The probiotic market, especially dairy products such as yogurts and fermented milks, has experienced rapid growth in Europe. The long-term exploitation of probiotics as health promoters is dependent on several factors, including sound, scientifically proven clinical evidence of health-promoting activity; accurate consumer information; effective marketing strategies; and, above all, a quality product that fulfills consumer expectations.

Bifidobacterium↗

PubMed2001

Lantibiotics: structure, biosynthesis and mode of action.

The lantibiotics are a group of ribosomally synthesised, post-translationally modified peptides containing unusual amino acids, such as dehydrated and lanthionine residues. This group of bacteriocins has attracted much attention in recent years due to the success of the well characterised lantibiotic, nisin, as a food preservative. Numerous other lantibiotics have since been identified and can be divided into two groups on the basis of their structures, designated type-A and type-B. To date, many of these lantibiotics have undergone extensive characterisation resulting in an advanced understanding of them at both the structural and mechanistic level. This review outlines some of the more recent developments in the biochemistry, genetics and mechanism of action of these peptides.

Alanine↗

PubMed2001

Direct in situ viability assessment of bacteria in probiotic dairy products using viability staining in conjunction with confocal scanning laser microscopy.

The viability of the human probiotic strains Lactobacillus paracasei NFBC 338 and Bifidobacterium sp. strain UCC 35612 in reconstituted skim milk was assessed by confocal scanning laser microscopy using the LIVE/DEAD BacLight viability stain. The technique was rapid (<30 min) and clearly differentiated live from heat-killed bacteria. The microscopic enumeration of various proportions of viable to heat-killed bacteria was then compared with conventional plating on nutrient agar. Direct microscopic enumeration of bacteria indicated that plate counting led to an underestimation of bacterial numbers, which was most likely related to clumping. Similarly, LIVE/DEAD BacLight staining yielded bacterial counts that were higher than cell numbers obtained by plate counting (CFU) in milk and fermented milk. These results indicate the value of the microscopic approach for rapid viability testing of such probiotic products. In contrast, the numbers obtained by direct microscopic counting for Cheddar cheese and spray-dried probiotic milk powder were lower than those obtained by plate counting. These results highlight the limitations of LIVE/DEAD BacLight staining and the need to optimize the technique for different strain-product combinations. The minimum detection limit for in situ viability staining in conjunction with confocal scanning laser microscopy enumeration was approximately 10(8) bacteria/ml (equivalent to approximately 10(7) CFU/ml), based on Bifidobacterium sp. strain UCC 35612 counts in maximum-recovery diluent.

Animals↗

PubMed2001

Naturally occurring lactococcal plasmid pAH90 links bacteriophage resistance and mobility functions to a food-grade selectable marker.

The bacteriophage resistance plasmid pAH90 (26,490 bp) is a natural cointegrate plasmid formed via homologous recombination between the type I restriction-modification specificity determinants (hsdS) of two smaller lactococcal plasmids, pAH33 (6,159 bp) and pAH82 (20,331 bp), giving rise to a bacteriophage-insensitive mutant following phage challenge (D. O'Sullivan, D. P. Twomey, A. Coffey, C. Hill, G. F. Fitzgerald, and R. P. Ross, Mol. Microbiol. 36:866-876; 2000). In this communication we provide evidence that the recombination event is favored by phage infection. The entire nucleotide sequence of plasmid pAH90 was determined and found to contain 24 open reading frames (ORFs) responsible for phenotypes which include restriction-modification, phage adsorption inhibition, plasmid replication, cadmium resistance, cobalt transport, and conjugative mobilization. The cadmium resistance property, encoded by the cadA gene, which has an associated regulatory gene (cadC), is of particular interest, as it facilitated the selection of pAH90 in other phage-sensitive lactococci after electroporation. In addition, we report the identification of a group II self-splicing intron bounded by two exons which have the capacity to encode a relaxase implicated in conjugation in gram-positive bacteria. The functionality of this intron was evident by demonstrating splicing in vivo. Given that pAH90 encodes potent phage defense systems which act at different stages in the phage lytic cycle, the linkage of these with a food-grade selectable marker on a replicon that can be mobilized among lactococci has significant potential for natural strain improvement for industrial dairy fermentations which are susceptible to phage inhibition.

Bacterial Proteins↗

PubMed2001

Strategy for manipulation of cheese flora using combinations of lacticin 3147-producing and -resistant cultures.

The aim of the present study was to develop adjunct strains which can grow in the presence of bacteriocin produced by lacticin 3147-producing starters in fermented products such as cheese. A Lactobacillus paracasei subsp. paracasei strain (DPC5336) was isolated from a well-flavored, commercial cheddar cheese and exposed to increasing concentrations (up to 4,100 arbitrary units [AU]/ml) of lantibiotic lacticin 3147. This approach generated a stable, more-resistant variant of the isolate (DPC5337), which was 32 times less sensitive to lacticin 3147 than DPC5336. The performance of DPC5336 was compared to that of DPC5337 as adjunct cultures in two separate trials using either Lactococcus lactis DPC3147 (a natural producer) or L. lactis DPC4275 (a lacticin 3147-producing transconjugant) as the starter. These lacticin 3147-producing starters were previously shown to control adventitious nonstarter lactic acid bacteria in cheddar cheese. Lacticin 3147 was produced and remained stable during ripening, with levels of either 1,280 or 640 AU/g detected after 6 months of ripening. The more-resistant adjunct culture survived and grew in the presence of the bacteriocin in each trial, reaching levels of 10(7) CFU/g during ripening, in contrast to the sensitive strain, which was present at levels 100- to 1,000-fold lower. Furthermore, randomly amplified polymorphic DNA-PCR was employed to demonstrate that the resistant adjunct strain comprised the dominant microflora in the test cheeses during ripening.

Bacterial Proteins↗

PubMed2001

Exploitation of plasmid pMRC01 to direct transfer of mobilizable plasmids into commercial lactococcal starter strains.

Genetic analysis of the 60.2-kb lactococcal plasmid pMRC01 revealed a 19.6-kb region which includes putative genes for conjugal transfer of the plasmid and a sequence resembling an origin of transfer (oriT). This oriT-like sequence was amplified and cloned on a 312-bp segment into pCI372, allowing the resultant plasmid, pRH001, to be mobilized at a frequency of 3.4 x 10(-4) transconjugants/donor cell from an MG1363 (recA mutant) host containing pMRC01. All of the resultant chloramphenicol-resistant transconjugants contained both pRH001 and genetic determinants responsible for bacteriocin production and immunity of pMRC01. This result is expected, given that transconjugants lacking the lacticin 3147 immunity determinants (on pMRC01) would be killed by bacteriocin produced by the donor cells. Indeed, incorporation of proteinase K in the mating mixture resulted in the isolation of transformants, of which 47% were bacteriocin deficient. Using such an approach, the oriT-containing fragment was exploited to mobilize pRH001 alone to a number of lactococcal hosts. These results demonstrate that oriT of pMRC01 has the potential to be used in the development of mobilizable food-grade vectors for the genetic enhancement of lactococcal starter strains, some of which may be difficult to transform.

Bacterial Proteins↗