Lactic acid bacteria (LAB) are utilized as a starter culture in the manufacturing of fermented dairy items, as a preservative for various food products, and as a probiotic. In our country, some research has been carried out, even if LAB plays a principal role in food preservation and improves the texture and taste of fermented foods, that is why we tried to evaluate their probiotic effect. The objective of this research was to determine the antibacterial activity of Lactococcus lactis (L. lactis) against Staphylococcus aureus (S. aureus) ATCC 29213, investigate their antioxidant activity, and characterize their sensitivity against 18 antibiotics. A total of 23 LAB (L. lactis subsp. cremoris, L. lactis subsp. Lactis diacetylactis, L. lactis subsp. lactis) were isolated from cow's raw milk. The antibacterial activity was performed using two techniques, competition for nutrients and a technique utilizing components nature, using the disk diffusion method. The sensitivity of the studied LAB to different antibiotics was tested on Man rogosa sharp (MRS) agar using commercial antibiotic disks. All strains of LAB were examined for their antioxidant activity. The antioxidant activity of L. lactis was tested by 2,2-diphenyl-1 picrylhydrazyl (DPPH). The results showed that the MRS medium was more adapted than Muller Hinton Agar (MHA) to investigate the antibacterial activity of L. lactis against S. aureus ATCC 29213. Also, L. lactis exhibited a notable degree of antibacterial activity against S. aureus ATCC 29213. L. Lactis subsp. Lactis displayed higher antibacterial activities, followed by L. lactis ssp. lactis biovar. diacetylactis, and lastly, L. lactis ssp. cremoris against S. aureus ATCC 29213. Lc 26 among all strains of L. lactis showed a high potential antibacterial activity reaching 40 ± 3 mm against S. aureus ATCC 29213. All strains of L. lactis showed a slightly moderate antioxidant activity (10.56 ± 1.28%-26.29 ± 0.05 %). The results of the antibiotic resistance test indicate that all strains of L. lactis were resistant to cefotaxime, sulfamethoxazole-trimethoprim, and streptomycin and were sensitive to Ampicillin, Amoxicillin, Penicillin G, Teicoplanin, Vancomycin, Gentamicin 500, Tetracycline, and Chloramphenicol. These test results indicate that this strain falls within the criteria of not posing any harmful effects on human health. The important antibacterial properties recorded for all L. Lactis strains were derived from the production of antibacterial active metabolites, such as protein, diacetyl, hydrogen peroxide, and lactic acid, together with the fight for nutrients. This study suggests that the strains of L. lactis could be added as an antibacterial agent against S. aureus ATCC 29213 and can provide an important nutritional property for their antioxidant potential.

Streptococcus thermophilus was considered one of the probiotic bacterial strains found in milk, cheese, and yogurt that provided health benefits to humans. Due to their probiotic potential, S. thermophilus can be very helpful in replacing chemical preservatives. This study came out to investigate the probiotic activity of different ten S. thermophilus isolates obtained from raw cow milk in eastern Morocco. The antimicrobial tests against multidrug-resistant bacteria (MDR): Staphylococcus aureus, and Escherichia coli were evaluated using the disc diffusion technique. In addition, the antioxidant potential was tested using the DPPH free radical assay. The bile salt tolerance was evaluated using M17 broth containing variable amounts of bile salt (0% as control; 0.1% and 0.3% as tests) at 37 °C for 3, 6 and 24 hours. Then cell counts were enumerated after 48 hours of incubation on M17 agar. Antibiotic susceptibility of S. thermophilus isolates against 20 antibiotics from 8 families (Rifamycins, Aminosides, Phenicols, Beta-lactam, Glycopeptides, Clindamycin, Cotrimoxazole, and Cyclines) were tested following a 24-hour incubation period using the antibiotic discs method. The diameters of the inhibition zones results were then compared to the recommendations made by the Antibiogram Committee of the French Microbiology Society of 2021. The results showed remarkable in vitro inhibitory ability of the S. thermophilus isolates against the tested multidrug-resistant bacteria S. aureus, confirming their potentiality as antibacterial agents. The mixtures of NaOH, catalase and proteinase K showed no inhibition zones against all tested multidrug-resistant bacteria, suggesting the main antibacterial effect of all isolates based on acids, hydrogen peroxide, and/or proteins. For the antioxidant activity, the DPPH inhibition values varied between 18.97% and 44.44% for the bacterial isolates ST9 and ST5, respectively. Notably, S. thermophilus isolates were able to survive up to 6 h of 37°C incubation with a bile salt concentration of 0.1%, where ST5 was the most promising isolate in terms of antioxidant activity. All isolates of S. thermophilus exhibited sensibility to all tested antibiotics except for rifampicin and trimethoprim-sulfamethoxazole compared to the European Committee on Antimicrobial Susceptibility Testing

Camembert is a French cheese characterized by a soft paste and a flowery rind. Morocco imports camembert cheese paste as a raw material. Today, Moroccan cheese manufacturers are looking to uncover the secrets associated with making Camembert cheese including the ones facilitating the smooth running of the stages of its manufacture. In Morocco, this type of cheese is scarce, not fully enumerated and no studies have been conducted on it as of yet. This is why we tried to manufacture this type of cheese in the laboratory to valorize it in Morocco due to its growing importance in the international market. The objective of this work is the optimization of the production of soft cheese with a flowery rind such as Camembert, while determining the quantity of microorganisms used for the fermentation of milk. Four types of industrial ferments with pre-established doses were used in addition to rennet. Fifteen cheese samples were made. The physico-chemical parameters checked during the manufacturing tests were fat content, pH and titratable acidity. The results show that the production of cheese requires the use of milk of good microbiological quality as well as the selection of specific ferments depending on the type of cheese to make. The best amount of the ferments used to make Camembert-type cheese during this work is: from 0.6% to 0.8% mesophilic if the viability rate is more than 3.73 x10², 0.3 % to 0.4% thermophilic if the viability rate is more than 3.95 x 10³, 1% to 5% yeast if the viability rate is more than 2.60 x 10³ , and 2% to 10% mesophilic if the viability rate is more than 3.30 x 10³. The most effective dose formula is two doses of Mesophiles for one dose of Thermophile. Or two doses of Penicillium Candidum mold for one dose of Geotrichum Candidum yeast. The microbiological quality of the milk used in this work and the cheese produced during this work is generally acceptable and conforms to Moroccan standards. During each Camembert production, whey quantity was measured. Cheese yield was determined by measuring cheese portions before and after ripening from a known quantity of milk. The sensory properties of dairy products are defined by their appearance, texture and flavor and are ultimately evaluated by tasting panels from the Agronomic and Veterinary Institute of Rabat.