Potential molecular mechanism of reuterin on the inhibition of Aspergillus flavus conidial germination: An in silico study

Reuterin is a natural antifungal agent derived from certain strains of Limosilactobacillus reuteri. Our previous study revealed that 6 mM reuterin inhibited completely the conidial germination of aflatoxigenic Aspergillus flavus. This study investigated the potential molecular mechanism of reuterin in inhibiting A. flavus conidial germination, which was pre-assumed that it correlated to the inhibition of some essential enzyme activity involved in conidial germination, specifically 1,3-β-glucan synthase, chitin synthase, and catalases (catalase, bifunctional catalase-peroxidase, and spore-specific catalase). The complex of 1,3-β-glucan synthase and chitin synthase with reuterin had a lower binding affinity than that with the substrate. Conversely, the complex of catalases with reuterin had a higher binding affinity than that with the substrate. It was suggested that 1,3-β-glucan synthase and chitin synthase tended to bind the substrate rather than bind reuterin. In contrast, catalases tended to bind reuterin rather than bind the substrate. Therefore, reuterin could be a potential inhibitor of catalases but may not be an inhibitor of 1,3-β-glucan synthase and chitin synthase. In this in silico study, we predicted that the potential molecular mechanism of reuterin in inhibiting A. flavus conidial germination was due to the inhibition of catalases activities by competitively binding to the enzymes active sites, thus resulting in the accumulation of reactive oxygen species in cells, leading to cells damage. PRACTICAL APPLICATION: This in silico study revealed that reuterin is a potential inhibitor of catalases in A. flavus, thereby interfering with the antioxidant system during conidial germination. This finding shows that reuterin can be used as an antifungal agent in food or agricultural products, inhibiting conidial germination completely.

Critical points and the presence of pathogenic bacteria in iced beverage processing lines

INTRODUCTION

Ice can be contaminated by pathogenic bacteria. This study aimed to identify critical points in iced beverage production and distribution lines to examine the presence of pathogenic bacteria in a beverage and its processing environment, as well as when water and ice used as main ingredients.

METHODOLOGY

The critical points were determined using the principles of Hazard Analytical Critical Control Point (HACCP) to analyze each processing and distribution step from the survey. Samples collected from the points of concern based on the critical points that were found were tested for pathogens by conventional method and molecular method using primers and polymerase chain reaction (PCR).

RESULTS

Escherichia coli was found in 6.34% of samples, and 0.7% of them were confirmed as enterotoxigenic Escherichia coli (ETEC) by PCR. Vibrio cholerae was found in in 0.7% of water samples used to make iced beverages and in ice production, as well as in 2.12% of distribution and production tools. Salmonella Typhimurium was found in 1.4% of water samples used to make ice and ice products. Staphylococcus aureus was found in 2.02% of the surfaces of ice distribution and production tools and in 5.05% of production and distribution workers' hands. S. aureus counts ranged from 2.4×102 - 3.5×102 colonies/100 cm² surface area and 1.9×10¹ - 3.7×102 colonies/workers' hands.

CONCLUSION

Control on many critical points in iced beverage processing and distribution is required so that the beverages are safe for consumption.

Physicochemical and Stability of Goat Cheese with Mono and Mixed Culture of Lactobacillus plantarum and Lactobacillus rhamnosus

The purpose of the study is to assess the effect of the use of mono probiotic culture and mixed cultures of Lactobacillus plantarum  and Lactobacillus rhamnosus  on the physicochemical properties and its viability during storage. The soft cheeses were made through three treatments: (1) the use of Lactobacilllus rhamnosus culture, (2) the use of Lactobacillus plantarum  culture and (3) the use of mixed cultures (Lactobacillus rhamnosus  and Lactobacillus plantarum). The variables measured were the cheese texture (firmness and stickiness), proximate, pH of the product, and the number of LAB. The results showed that cheese firmness ranged from 10.78 to 47.75 gf, cheese stickiness was -8.23 to -11.53 gs, cheese pH was 4.70 - 5.60; number of cheese LAB was 8:59 - 9.69 log cfu/g. The content of protein, fat, and ash were 13.65-16.54%, 15:28-20:03%, and 2.7-3.39%, respectively. The conclusion of this study was that the soft cheeses with mixed cultures of L.rhamnosus  and L.plantarum are potentially good to be developed as a probiotic food.

Physicochemical and Stability of Goat Cheese with Mono and Mixed Culture of Lactobacillus plantarum and Lactobacillus rhamnosus

The purpose of the study is to assess the effect of the use of mono probiotic culture and mixed cultures of Lactobacillus plantarum  and Lactobacillus rhamnosus  on the physicochemical properties and its viability during storage. The soft cheeses were made through three treatments: (1) the use of Lactobacilllus rhamnosus culture, (2) the use of Lactobacillus plantarum  culture and (3) the use of mixed cultures (Lactobacillus rhamnosus  and Lactobacillus plantarum). The variables measured were the cheese texture (firmness and stickiness), proximate, pH of the product, and the number of LAB. The results showed that cheese firmness ranged from 10.78 to 47.75 gf, cheese stickiness was -8.23 to -11.53 gs, cheese pH was 4.70 - 5.60; number of cheese LAB was 8:59 - 9.69 log cfu/g. The content of protein, fat, and ash were 13.65-16.54%, 15:28-20:03%, and 2.7-3.39%, respectively. The conclusion of this study was that the soft cheeses with mixed cultures of L.rhamnosus  and L.plantarum are potentially good to be developed as a probiotic food.