Background and objective:

Bacteria of the Genus Kocuria are found in several environments and their isolation from foods has recently increased due to more precise identification protocols using molecular and instrumental techniques. This review describes biotechnological properties and food-linked aspects of these bacteria, which are closely associated with clinical cases.

Results and conclusion:

Kocuria spp. are capable of production of various enzymes, being potentially used in environmental treatment processes and clinics and production of antimicrobial substances. Furthermore, these bacteria show desirable enzymatic activities in foods such as production of catalases and proteases. Beneficial interactions with other microorganisms have been reported on increased production of enzymes and volatile compounds in foods. However, there are concerns about the bacteria, including their biofilm production, which generates technological and safety problems. The bacterial resistance to antimicrobials is another concern since isolates of this genus are often resistant or multi-resistant to antimicrobials, which increases the risk of gene transfer to pathogens of foods.

Background and objective:

Food-producing animals can potentially transmit resistant bacterial pathogens to humans with various rates in various microbial species. Confronting the global antimicrobial resistance challenges needs collaboratively collective efforts by countries. Published literatures regarding antimicrobial resistance challenges and surveillance continually increase worldwide. Furthermore, understanding of antimicrobial resistance challenges and surveillance must be improved. Therefore, this brief review included antimicrobial resistance fundamentals and prevention mechanisms and its global surveillance trends specific to animal-food-human pathways.

Results and Conclusions:

The capacity of antimicrobial resistance to include economic and health effects on various regions of the world must not be underestimated. The nature of antimicrobial resistance mechanisms contributes to its complicated spread mechanisms. Hence, there is the need for effective and efficient methods or strategies to challenge antimicrobial resistance. In addition to the concerns of antimicrobial agents with the developed understanding of the antimicrobial resistance prevention mechanisms, key facts of surveillance, specifically in microbiological contexts, are demonstrated in this review. In recent decades, global surveillance trends have been urged to overcome antimicrobial resistance problems. Due to its complexities, antimicrobial resistance remains a major public health concern with no single strategy to thoroughly prevent emergence or spread of infectious microorganisms.

Background and Objective:

Consumption of milks fermented with lactic acid bacteria has been shown to improve lipid profiles; however, the mechanisms underlying this improvement are not clear. Using in vitro analyses, the aim of this study was to investigate how Lactobacillus casei strains AP and AG assimilate cholesterol.

Materials and Methods:

Bacterial growth in ox gall-supplemented media, quantity of assimilated cholesterol and activity of bile salt hydrolase were assessed in Lactobacillus casei strains AP and AG. Furthermore, cholesterol attachment to cell walls was assessed using scanning electron microscopy.

Results and Conclusions:

Lactobacillus casei AG showed a higher cholesterol assimilation (13.05 mg dl^-1 ±0.48) than Lactobacillus casei AP (8.05 mg dl^-1 ±0.48) as well as a faster growth rate of the former strain that that of the latter one. Growth inhibition of Lactobacillus casei AP was associated with increased activity of bile salt hydrolase (halo size of 1.62 mm ±0.20), compared to that of Lactobacillus casei AG (1.37 mm ±0.07) and upregulation of the bsh gene. High cholesterol assimilations by Lactobacillus casei AG seem to attribute to membrane attachment via resistance to bile acids.

Background and Objective:

Vanillin is a strong flavor used widely in food industries, but the quantity of this compound from plant sources is minimal. In the present study, vanillin was produced as bio-vanillin using biotechnological techniques and effects of the process parameters (carbon-source, nitrogen-source and pH) on ferulic acid bioconversion to vanillin for enhancing vanillin concentration were studied using Bacillus aryabhattai NCIM 5503.

Material and Methods:

Briefly, culture media included 5 g l^-1 each carbon (glucose, sucrose, fructose, sorbitol, lactose, xylitol and mannitol) and nitrogen (ammonium sulphate, peptone, beef extract, yeast extract and urea) sources in distilled water supplemented with 5% (w v^‑1) of ferulic acid and 1% (v v^-1) of Bacillus aryabhattai NCIM 5503 as inoculum at a pH range of 4.5-12. Fermentation broth was extracted using centrifuge and further analyzed for the presence of vanillin using spectrophotometry and high-performance liquid chromatography.

Results and conclusion:

This study revealed that a maximum vanillin concentration of 0.87 g l^-1 was achieved under optimum conditions (culture media with fructose and beef extract at pH 9) of 30 ºC and 150 rpm. Furthermore, vanillin in the extracted fermented broth was characterized using high-performance liquid chromatography and spectrophotometric analysis with thiobarbituric acid assay at 55 ºC for 10 min followed by 20 min of incubation at room temperature.

Background and Objective:

Antibacterial compounds produced by lactic acid bacteria are believed to replace functions of chemical preservatives. The objectives of this study were to identify lactic acid bacteria, which produced antibacterial compounds, from fermented durian flesh (tempoyak) and to assess antibacterial activities of the isolates.

Material and Methods:

Two bacterial identification techniques were used, including API 50 CHL kit with supplementary medium and matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-TOF/MS).

Results and Conclusion:

Four various lactic acid bacteria strains of Lactobacillus buchneri, Lactobacillus plantarum, Lactobacillus brevis I and Lactobacillus acidophilus I were identified using API 50 CHL Kit and five various others of Lactobacillus paracasei DSM 2649, Lactobacillus buchneri DSM 20057T, Lactobacillus parabuchneri DSM 57069, Lactobacillus paracasei DSM 20020 and Lactobacillus farcimini CIP 103136T using MALDI-TOF/MS. Cell-free supernatant extracted from Lactobacillus plantarum, Lactobacillus buchneri, Lactobacillus brevis I and Lactobacillus acidophilus I included strong inhibitory effects against Vibrio cholera O1 (Inaba type), Vibrio cholera O139 (Bengal type), Vibrio parahaemolyticus ATCC 17802, Escherichia coli ATCC 11795, Escherichia coli O157, Salmonella typhimurium ATCC 14028 and a total of 23 serotypes of Salmonella spp. associated with outbreaks of food poisoning from raw chicken, egg shell and water samples. Only Lactobacillus buchneri DSM 20057T was identified by MALDI-TOF/MS as a strain producing sorbic and benzoic acids. This strain can potentially be used as food preservative to decrease growth of foodborne pathogenic bacteria.

Background and Objective: Induced mutagenesis is widely used to produce novel mutants with improved productivities. Ethyl methane-sulfonate-induced mutagenesis followed by intergeneric protoplast fusion were used to develop lactic acid bacterial strains with high antimicrobial activities.

Materials and Methods:

The antagonistic activities of seven LAB strains were assessed against seven indicator microorganisms using well diffusion assay. The highest two producers were subjected to ethyl methane-sulfonate mutagenesis followed by intergeneric protoplast fusion. Selection of the mutants and the fusants from the suggested fusion cross was based on the responses to different antibiotics.

Results and Conclusion:

Lactococcus lactis subsp. lactis and Bifidobacterium longum showed the highest antimicrobial activities against most of the indicator microorganisms. Such activities were achieved at pH 2.0 and dramatically decreased by increasing the pH level. Ethyl methane-sulfonate-induced mutagenesis resulted in thirty mutants, four of which exhibited higher activities than their wild type parental strains (two for each parent). In an attempt to increase such activity, intergeneric protoplast fusions between LM 13 (resulting from Lactococcus lactis subsp. lactis) and BM 4 (resulting from Bifidobacterium longum) mutants were carried out. Twelve fusants were obtained. Interestingly, one fusant (F1) showed an increase in antimicrobial activity, compared to its parental strains. An increased range of 58.1 to 345.7% compared to the parental strain Lactococcus lactis subsp. lactis and a range of 51.5 to 168.5% for the second parental strain were noticed. The LM 13, LM 6, BM 4 and BM 12 mutants and the F1 fusant can be used in the preservation of food products.

Background and Objective: Currently, no published studies are available that compare central limit theorem model with traditionally used growth models in predictive food microbiology to describe bacterial growth behaviors of Pseudomonas spp. in beefs. The major objectives of the present study were to develop a novel growth model based on the central limit theorem and compare the prediction capability of the model with those of various growth models (modified Gompertz, logistic, Baranyi and Huang models) commonly used in predictive food microbiology.

Material and Methods: Bacterial growth data for Pseudomonas spp. were collected from previously published studies on beefs stored at isothermal storage temperatures (0, 4, 7, 10, 15 and 20 °C). Temperature dependent kinetic parameters (maximum specific growth rate ‘µ_max’ and lag phase duration ‘λ’) collected from various primary models were described as functions of storage temperatures using Ratkowsky model. Fitting capability of the novel growth model based on the central limit theorem was compared with other growth models using mean square error and coefficient of determination.

Results and Conclusion: The novel growth model developed in this study provided mean square errors less than 0.104 and coefficients of determination greater than 0.962. No significant differences (p>0.05) were seen between the statistical indices of this developed model and traditionally used growth models. Results have shown that the novel growth model based on the central limit theorem can be used to describe the growth behaviors of microorganisms as alternative to traditionally used growth models of modified Gompertz, logistic, Baranyi and Huang models in predictive food microbiology. Furthermore, this novel model can be used for the prediction of shelf-life of beefs as a function of temperature since spoilage of beefs is directly linked to the load of Pseudomonas spp.

Background and objective: Nowadays, novel biotechnological methods are preferred for flavoring productions since traditional methods include disadvantages. The aim of this study was to assess in situ biosynthesis of natural fruity flavors in fermented milks using microbial co-cultures and lipase enzyme.

Materials and methods:

Trans esterification of milk fats with ethanol was carried out to develop fruity flavors in ultra-high-temperature whole milks using lipase of Palatase coupled with ethanol fermentation. Kluyveromyces marxianus NCYC 1425 was used to produce in situ ethanol in co-cultures with Lactobacillus fermentum PCC or Lactobacillus paracasei L26. Effects of co-culturing on cell viability and fermentation progress were assessed using enumeration of viable cells and measurement of pH in samples at 0, 24 (Palatase addition) and 48 h (end of fermentation). Headspace solid phase microextraction-gas chromatography (SPME)-MS/FID was used for ester, ethanol and free fatty acid analyses at the beginning and end of the fermentation. Standard curve of ethanol was used to assess the products in terms of being Halal.

Results and conclusion:

Kluyveromyces marxianus included synergistic effects on Lactobacillus paracasei growth as well as antagonistic effects on Lactobacillus fermentum growth. Antimicrobial effects were seen in Kluyveromyces marxianus-Lactobacillus paracasei co-cultures when Palatase was added. Palatase significantly increased ester levels of the fermented samples. The co-cultures did not include significant differences in shorter chain ester levels (esters of 4-7 carbon chain fatty acids); in contrast, Kluyveromyces marxianus- Lactobacillus fermentum resulted in higher levels of longer chain esters. Although the Kluyveromyces marxianus cultures resulted in higher ester levels compared to that its co-cultures did, the cultures can be used as appropriate adjunct cultures with Lactobacillus cultures to boost flavor ester synthesis. This flavor synthesis can be an appropriate alternative for artificial flavoring agents.