applied food biotechnology
Volume:8 Issue: 2, Spring 2021

Bacteria of the Genus Kocuriaare 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.

Kocuriaspp. 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

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.

Thecapacity of antimicrobial resistance to include economicand 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 needfor effectiveandefficient methods or strategies to challenge antimicrobial resistance. In addition to the concerns of antimicrobial agents withthedeveloped understanding of the antimicrobial resistance prevention mechanisms, key facts of surveillance, specifically in microbiological contexts, aredemonstrated in this review. In recent decades, global surveillance trends have been urged to overcome antimicrobial resistance problems. Due to its complexities,antimicrobial resistance remainsa major public health concern with no single strategyto thoroughly prevent emergence or spread of infectious microorganisms.

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 vitroanalyses, the aim of this study was to investigate how Lactobacillus caseistrains AP and AG assimilate cholesterol.

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.

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

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 usingbiotechnological techniques and effectsof theprocess parameters (carbon-source, nitrogen-source and pH) on ferulic acid bioconversion to vanillin for enhancing vanillin concentrationwere studiedusing Bacillus aryabhattaiNCIM 5503.

Briefly, culture media included 5 g l-1each 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 apH 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.

This study revealed that a maximum vanillin concentration of 0.87 g l-1was achieved under optimum conditions(culture media with fructose and beef extract at pH 9) of30 ºCand 150 rpm. Furthermore, vanillin in the extracted fermented broth was characterized using high-performance liquid chromatographyand spectrophotometric analysis with thiobarbituric acid assay at 55 ºC for 10 min followed by 20 min of incubation at room temperature.

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, whichproduced antibacterial compounds, from fermented durian flesh (tempoyak) and to assess antibacterial activities of the isolates.

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

Four various lactic acid bacteria strains of Lactobacillus buchneri, Lactobacillusplantarum, LactobacillusbrevisI and LactobacillusacidophilusI were identified using API 50 CHL Kitand five various others of LactobacillusparacaseiDSM 2649, LactobacillusbuchneriDSM 20057T, LactobacillusparabuchneriDSM 57069, LactobacillusparacaseiDSM 20020 and LactobacillusfarciminiCIP 103136T using MALDI-TOF/MS. Cell-free supernatant extracted from Lactobacillusplantarum, Lactobacillusbuchneri, LactobacillusbrevisI and LactobacillusacidophilusI included strong inhibitory effects against Vibrio choleraO1 (Inaba type), Vibrio choleraO139 (Bengal type), Vibrio parahaemolyticusATCC 17802, Escherichia coliATCC 11795, Escherichia coliO157, Salmonella typhimurium ATCC 14028 and a total of 23 serotypes of Salmonellaspp. associated with outbreaks of food poisoning from raw chicken, egg shell and water samples. Only LactobacillusbuchneriDSM 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.

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.

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.

Lactococcus lactis subsp.lactisand Bifidobacterium longumshowed 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 lactissubsp.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 itsparental strains. An increased range of 58.1 to 345.7% compared to the parental strain Lactococcus lactissubsp.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

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 Pseudomonasspp. 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.

Bacterial growth data for Pseudomonasspp. 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 ‘μmax’ 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.

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 statisticalindices 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 thegrowth 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 linkedto the load of Pseudomonasspp.

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

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 marxianusNCYC 1425 was used to produce in situethanolin 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.

Kluyveromyces marxianus included synergisticeffects on Lactobacillus paracaseigrowth as well as antagonistic effects on Lactobacillusfermentumgrowth. Antimicrobial effects were seen in Kluyveromyces marxianus-Lactobacillusparacaseico-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-Lactobacillusfermentumresulted in higher levels of longer chain esters. Although the Kluyveromyces marxianuscultures resulted in higher ester levels compared to that its co-cultures did,the cultures can be used as appropriate adjunct cultures with Lactobacilluscultures to boost flavor ester synthesis. This flavor synthesis can be an appropriate alternative for artificial flavoring agents.