Lactic Acid Bacteria as Biological Control of Staphylococcus aureus in Coalho Goat Cheese

Antistaphylococcaland antioxidant activities of bacteriocinogeniclactic acid bacteriaand essential oil in goat coalho cheese

AIMS

Bacteriocinogenic lactic acid bacteria (LAB) isolates and Croton heliotropiifoliusessential oil (EO) were used to inhibit Staphylococcus aureussubsp.aureusand enhance the antioxidant action in goat coalhocheese (GCC).

METHODS AND RESULTS

LAB isolates were selected for their inhibitory capacity against S. aureus subsp. aureus, safety, existence of bacteriocin-encoding genes, bacteriocinogenic activity, and its antistaphylococcal action. The staphylococcal inhibition capacity of C. heliotropiifolius EO was also verified.Three cheeses were prepared containing: S. aureussubsp.aureus (GCC SA),S. aureussubsp.aureus+ LAB (GCC SA+LAB), and S. aureussubsp. aureus+ EO (GCC SA+EO). Samples were analyzed on days 0, 7, 14 and 21. Based on the screening, three LAB isolates were selected and identified as Enterococcus faecium. In GCC, the smallest population of S. aureussubsp.aureuswas found until the 17th in the GCC SA+EO and from the 18th in the GCC SA+LAB. Total phenolic content (TPC) and antioxidant activity increased over time in GCCs.

CONCLUSIONS

Autochthonous bacteriocinogenic LAB and C. heliotropiifolius EO are natural resources of the Caatinga, an exclusively Brazilian biome that predominates in the Northeast of the country, with the potential to reduce the presence of S. aureus and increase the antioxidant activity in the GCC.

SIGNIFICANCE AND IMPACT OF THE STUDY

GCC is a product of cultural importance in northeastern Brazil. The process of obtaining the GCC is manual and there is a high frequency of S. aureus in the product. Resources of the Caatinga with biofunctional properties can be tested to reduce the risk of staphylococcal toxins, and contribute to the nutritional value of the GCC, maintaining regional characteristics and respecting the local cultural tradition. LAB and C. heliotropiifolius EO contribute to the incorporation of bioactive substances and microbiological quality, generating a value-added GCC with exclusive resources ofthe Caatinga.

Use of encapsulated lactic acid bacteria as bioprotective cultures in fresh Brazilian cheese

There is great interest for biopreservation of food products, and encapsulation may be a good strategy to extend the viability of protective cultures. In this study, Lactobacillus paraplantarum FT-259 and Lactococcus lactis QMF 11 were separately encapsulated in casein/pectin (C/P) microparticles, which were tested for antilisterial and anti-staphylococcal activity in fresh Minas cheese (FMC) stored at 8 °C. The encapsulation efficiency for both lactic acid bacteria (LAB) was 82.5%, with viability over 6.2 log CFU/g after storage of C/P microparticles for 90 days under refrigeration. Interestingly, free Lb. paraplantarum and free Lc. lactis grew significantly in refrigerated FMC, both in the presence and absence of pathogens, but only the first significatively grew when encapsulated. Encapsulation increased the antilisterial activity of Lb. paraplantarum in FMC. Moreover, Lc. lactis significantly inhibited listerial growth in FMC in both its free and encapsulated forms, whereas Staphylococcus aureus counts were only significantly reduced in the presence of free Lc. lactis. In conclusion, these results indicate that C/P microparticles are effective carriers of LAB in FMC, which can contribute for the assurance of the safety of this product.

Antimicrobial Potential of Food Lactic Acid Bacteria: Bioactive Peptide Decrypting from Caseins and Bacteriocin Production

Lactic acid bacteria (LAB) potential in the food industry and in the biotechnological sector is a well-established interest. LAB potential in counteracting especially food-borne infections has received growing attention, but despite being a road full of promises is yet poorly explored. Furthermore, the ability of LAB to produce antimicrobial compounds, both by ribosomal synthesis and by decrypting them from proteins, is of high value when considering the growing impact of multidrug resistant strains. The antimicrobial potential of 14 food-derived lactic acid bacteria strains has been investigated in this study. Among them, four strains were able to counteract Listeria monocytogenes growth: Lactococcus lactis SN12 and L. lactis SN17 by high lactic acid production, whereas L. lactis 41FLL3 and Lactobacillus sakei I151 by Nisin Z and Sakacin P production, respectively. Strains Lactococcus lactis MG1363, Lactobacillus rhamnosus 17D10 and Lactobacillus helveticus 4D5 were tested and selected for their potential attitude to hydrolyze caseins. All the strains were able to release bioactive peptides with already known antimicrobial, antihypertensive and opioid activities. These features render these strains or their bioactive molecules suitable for use in food as biocontrol agents, or as nutraceutical supplements to treat mild disorders such as moderate hypertension and children insomnia. These results highlight once again that LAB potential in ensuring food safety, food nutraceutical value and ultimately in favoring human health is still underexplored and underexploited.

Bacterial Succession through the Artisanal Process and Seasonal Effects Defining Bacterial Communities of Raw-Milk Adobera Cheese Revealed by High Throughput DNA Sequencing

The bacterial community of the artisanal Adobera cheese from Los Altos de Jalisco was described through high-throughput sequencing of 16S rRNA gene libraries. Samples were collected in two different seasons (dry and rainy) during four key steps of the manufacturing process (raw milk, fresh curd, matured curd, and cheese). Bacterial diversity was higher in early steps in comparison with the final elaboration stages. Firmicutes and Proteobacteria were the most abundant phyla, strongly represented by the Streptococcaceae, Enterobacteriaceae and Lactobacillaceae families, and core bacteria genera such as Streptococcus spp., Lactococcus spp., and Lactobacillus spp. Undesirable bacteria, including Pseudomonas spp. and Acinetobacter spp., were also detected in raw milk but almost undetectable at the end of the cheese manufacturing process, and seemed to be displaced by lactic-acid bacteria-related genera. Seasonal effects were observed on the community structure but did not define the core microbiota composition. Predictive metabolism was related to membrane transport, and amino-acid, lipid, and carbohydrate metabolism pathways. Our results contribute to deduce the role of bacteria involved in Adobera cheese manufacturing in terms of the metabolism involved, cheese microbial safety, and how undesirable bacterial populations could be regulated by process standardization as a potential tool to improve safety.

Microbiota of Sardinian Goat's Milk and Preliminary Characterization of Prevalent LAB Species for Starter or Adjunct Cultures Development

This work was performed to study the microbiota of raw goat's milk (67 samples) collected in different areas of Sardinia, in order to select autochthonous lactic acid bacteria (LAB) strains for use in goat cheese manufacturing. Total mesophilic bacteria ranged between 10⁵ and 10⁷ cfu/mL; mean counts of Enterobacteriaceae did not exceed 4 log cfu/mL whereas those of E. coli and coagulase-positive staphylococci were lower than 1.5 and 2 log ufc /ml, respectively. Neither Salmonella spp. nor Listeria monocytogenes were recovered. The numbers of total LAB were in the range from 10⁴ to 10⁷ cfu/mL and mean yeasts counts varied between 10³ and 10⁵ cfu/mL. The most frequently isolated LAB species were Lactococcus lactis subsp. lactis and Lactobacillus paracasei. The presence of Enterococcus faecium was also noteworthy. The in vitro study of some functional characteristics related to technological properties of the strains belonging to these species allowed to point out some strains possessing good potential for use as adjunct or starter cultures in the production of cheese.