The importance of the antibacterial resistant bacteria in the hide/skin soaking process has been emphasized due to their destructive properties on finished leather.Lichens may be a solution to overcome this resistance problem.Isolate 1 from soak liquor samples was assigned to Enterococcus durans (99.86%).For screening of possible antibacterial effects of lichen acetone extracts, six lichen species (Hypogymnia tubulosa, Hypogymnia physodes, Evernia divaricata, Pseudevernia furfuracea, Parmelia sulcata and Usnea sp.) were examined by nine-fold dilution against E. durans. H. tubulosa, H. physodes, and E. divaricata extracts showed antibacterial effects at the concentrations of 240,120 and 60 µg/mL whereas the extracts of P. furfuracea had an antibacterial effect at 240 and 120 µg/mL.On the other hand, P. sulcata had no antibacterial effect. The most successful lichen extract was determined to be Usnea sp. at the concentrations of 240,120,60,30 and 15 µg/mL.In conclusion, lichen extracts seem to have potential antibacterial efficacies against E. durans.

Long-term or improper use of antibacterial agents utilized in the soaking process has led to the resistance of some bacteria in the leather industry. New agents may be the solution to combat these antibacterial resistant bacteria in the soaking process. As a natural resource, lichens are known to have many biological activities. In previous studies, we demonstrated that the acetone extracts of several lichen species including Usnea sp. may have potential antibacterial and anti–biofilm properties against some Bacillus species, which were isolated from different soak liquor samples. In the present study, it was questioned whether the same bioactivities of acetone extracts of Usnea sp. can be seen in the mixed cultures of tank surface samples and pre-and main soak liquor samples, which were obtained from different tanneries. Although the extracts did not show noteworthy antibacterial effect against one of the tank surface samples (inhibition ratios; 6.5–16.22 %), inhibition percentages were detected as 69.32 and 46.33 at the concentrations of 240 and 120 µg/mL for the other tank surface sample. The anti-biofilm potential of the extracts was tested on the sample where the antibacterial activity of the extracts was not observed. One of the mixed culture of samples from the tank surface could not be inhibited by the extracts in terms of bacterial growth. However, the extracts were tested on this biofilm-forming sample and detected more than 50% inhibition. Furthermore, the extracts inhibited the growth of the mixed culture of bacteria from pre-soak liquor by the percentages of 78.96, 61.5, 51.3, 45.1, and 33.4 at the concentrations of 240, 120, 60, 30 and 15 µg/mL, respectively. On the other hand, the same antibacterial efficacy could not be observed in the other mixed culture from pre-soak liquor sample obtained from a different tannery whereas this sample formed a biofilm structure. The mixed culture of samples from the main soaking process was inhibited by the extracts at the inhibition percentages of 62.13–78.17 at the concentrations of 240- 30 µg/mL. Similar results were also obtained for the other sample (64.6–76.5%) from main soak liquor sample obtained from a different tannery. In conclusion, lichen extracts may have potential antibacterial and anti-biofilm properties against the mixed culture of bacteria from tank surface, pre-and main soak liquor samples and maybe alternatively utilized in the leather industry.

Bacteria forms biofilm to be resistant to antibacterial agents and other unfavorable environment as compared to planktonic bacterial cells. Due to resistance of bacterial biofilms to commonly used antimicrobial agents and adverse effects of these biofilms in different industries, potential natural compounds which can inhibit bacterial biofilms have attracted more attention in recent years. Lichens are known to have unique secondary metabolites with various biological activities including anti-biofilm properties. Therefore, Bacillus toyonensis, Bacillus mojavensis, Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus velezensis, Bacillus cereus, and Bacillus licheniformis, isolated from soak liquor samples in the previous study, were tested for their ability to form biofilm in this study. Biofilm-forming Bacillus species were detected as B. subtilis, B. amyloliquefaciens, and B. velezensis. The anti-biofilm effect of the acetone extracts of Usnea sp. was evaluated at various concentrations against these biofilm-forming isolates. The anti-biofilm effect of acetone extracts of Usnea sp. against B. subtilis and B. amyloliquefaciens was observed at the concentration of 5 µg/mL by inhibition ratios of 62.75% and 72.72%, respectively. In addition, biofilm formation of B. velezensis was inhibited by the treatment with 1.25 µg/mL extracts at a 62.69% inhibition rate. Biofilm formations of B. amyloliquefaciens and B. velezensis were also suppressed by the extracts at varying percentages of inhibition ranging between 10.11-43.69% and 21.25-46.35%, respectively. This study may provide an alternative approach to overcome the biofilm formation and bacterial resistance to the antibacterial agents in the leather industry.

The increase in the incidence of foodborne diseases has been demonstrated by epidemiological studies, and the adverse impact on the socio-economic development of countries has been also reported by health authorities. The combat against foodborne pathogens through the use of natural biosources has become the focus of recent research. Lichens produce several secondary metabolites with various biological activities including antibacterial, antifungal, anti-cancer etc. due to competition with other living things in their surrounding environment. In this perspective, we aimed to investigate the antibacterial properties of Usnea sp. that collected from Kastamonu, Turkey against five foodborne pathogens in the present study. These tested bacteria included both Gram-positive and Gram-negative ones. Our data demonstrated that the acetone extracts of Usnea sp. had antibacterial efficiencies especially against Gram-positive bacteria tested (C. perfringens, S. aureus, and B. cereus) at varying percentages. This potential antibacterial activity of Usnea sp. suggests that it can be used in the food industry. Since it has already been reported to be used in dishes or ingredients of bread, it gives the idea that it may be used as a food additive (such as a preservative, extending shelf life). However, detailed studies for its toxicity or the dosages that do not be toxic should be done.

Food safety is of great importance all over the world as it concerns consumer health. All employees in the food chain must comply with the hygiene rules. One of the important issues that threaten food safety is contamination with microorganisms. Numerous people are affected by contaminated and/or poorly preserved food and outbreaks have occurred. The World Health Organization (WHO) draws attention to human health and economic losses in this respect. From ancient times, herbs and spices are utilized in Turkey and various parts of the world and improved the flavor of food and their sensory properties. It is also possible to prevent the development of Staphylococcus aureus, which causes food poisoning, thanks to the antibacterial properties of culinary herbs or spices. Natural antimicrobial substances from spices and herbs may be alternative strategies in inhibition/elimination of growth of and in food preservation of S. aureus extending the shelf life without synthetic preservatives. This review aims to explain foodborne diseases and their global burden, staphylococcal food poisoning, natural antimicrobials, some edible herbs in Turkey: their culinary uses and antibacterial efficacy against S. aureus.