مجله میکروبیولوژی کاربردی در صنایع غذایی
سال چهارم شماره 3 (پاییز 1397)

In this study, chitosan was glycosylated with sugars glucose, maltose and starch through the non-enzymatic Maillard browning reaction at 121 °C for 15 min. The effect of sugars molecular weight on pH changes, intermediate and final (melanoidins) products of the Maillard reaction, antioxidant activity and as well as antimicrobial effect (disk diffusion method, well diffusion method, minimum inhibitory concentration, and minimum bactericidal/fungicidal concentration) of the obtained conjugates were evaluated. Glycosylation reaction led to a significant reduction in pH value of all chitosan-sugar systems (p<0.05) and chitosan-glucose conjugate showed the lowest pH value. Intermediate and final products of the Maillard reaction were significantly increased and the trend was pronounced in chitosan-glucose system than other systems. Antimicrobial activity of the conjugates obtained from chitosan and different sugars against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger improved after the Maillard reaction. Based on DPPH radical scavenging (DPPH-RS) activity and reducing power assays, antioxidative capacity of all samples increased after thermal process. It can be concluded from the results of this communication that chitosan conjugates based on the Maillard reaction can be applied as food-born antioxidant and antimicrobial agents to boost shelf-life of many food products as well as to design novel functional foods containing biologically active components.

The purpose of present research is the comparison of two new methods of ochratoxin detection i.e. cadmium tellutide quantum dot and nanoparticle magnetic silica based on fluorescence resonance energy transfer (FRET) from cadmium telluride quantum dot to RHo123. Nano particle magnetic silica was synthesized using FeCl3 and FeSO4 under nitrogen flow, alkaline pH and addition of TEOS solution. As a new method, in order to add a functional group, we used APTES, and to increase these groups and elevate its effectiveness, it was subjected to glutaraldehyde. The specific immune-reaction between the anti-ochratoxin antibody on the quantum dot and the labeled-ochratoxin brings the Rho 123 fluorophore (the acceptor), and the quantum dot (the donor (in close spatial proximity and causes FRET to occur upon photo-excitation of the quantum dot. In the absence of unlabeled ochratoxin, the antigen-antibody complex is stable and strong emission of quantum dot is observed. In the presence of free ochratoxin, it will compete with the rhodamine labeled ochratoxin -albumin complex (as a bionanosensor) for binding to the antibody- quantum dot conjugate, and thus, FRET is increasingly suppressed. There is a linear relationship between the decreased fluorescence intensity of Rho 123 in 580nm with increasing concentration of ochratoxin present in the sample in the range 8 - 48 pg /ml. By using the magnetic silica Nano particle, a signal intensifier rise sensitivity of the system from 22 to 0.8pg/ml, which is a 275-fold increase. This highly sensitive homogenous competitive detection is simple, rapid and efficient. It does not require multiple separation steps as well as excessive washing.

Chemical fungicide is the most affordable and easiest way to fight against plant diseases, but they increase concerns about endangering human health and residual in the environment. Barley is one of the most important and consumable cereals in the world. Plant essential oils are volatile compounds from plants that have strong antimicrobial properties with phenolic and antioxidant components. The aim of this study was to investigate the four plant essential oil including Savory, Thyme, Rosemary and Fennel on the growth and production of ochratoxin of Aspergillus ochraceus pathogen in barly. In this study, the effect of four plant essential oils (Satureja khuzestanica, Thymus daenensis, Rosmarinus officinalis, Foeniculum vulgare) on the growth pathogen in the petri dishes and the level of ochratoxin A produced by A. ocraceus was investigated in addition, it was studied the essential oils effect on ochratoxin in the culture medium. Measuring of ochratoxin was performed by High Performance thin-layer chromatography. The results of this study showed that the essential oils can significantly decrease the growth of the A. ocraceus and the production of ochratoxin by the pathogen. Savory essence at a concentration of 250 μg/ml inhibits the production of detectable ochratoxin in the medium by preventing the growth of the pathogen. In this concentration, essential oils of Rosemary and Thyme were 79.1% and 53.2% respectively, and the dry weight of the fungi decreased completely. Rosemary essential oil at the highest applied concentration (1000 μg/ml) did not inhibite it was investigated the growth of the pathogen it was investigated, but prevented the production of toxin. Essential oils of Savory, Thyme, Rosemary and Fennel showed fungicidal properties. These essential oils affect the ochratoxin and degrade it in the culture medium.

Increasing the survivability of probiotic bacteria that are exposed to the severe conditions of food and gastrointestinal tract, is always one of the concerns of scientists in the field of food and medicine. Hence, microencapsulation of probiotics has been proven as a novel technique for increasing probiotic tolerance in gastrointestinal simulation conditions. In this research, microencapsulation of Lactobacillus plantarum (A7 & S2G) with three different matrix materials (M1, M2, M3) was performed to increment the bacterial viability in simulated gastric fluid and porcine bile salt solution condition. Microencapsulation efficiency of Lactobacillus plantarum (A7 & S2G) in M1, M2 and M3 matrices was (98.72, 90.16 %), (95.29, 98.52 %) and (98.10, 93.07 %), respectively. Microcapsules were placed in simulated gastrointestinal condition for 10, 60, 120 min at 37 °C. Also, the survivability of microcapsulated probiotic bacteria was investigated at 4 and 25 °C during 8 weeks. The results of this study showed that the population reduction ratio of microencapsulated bacteria to free cells in matrices (M1, A7), (M2, A7), (M3, A7), (M1, S2G), (M2, S2G) and (M3, S2G) in simulated stomach condition was obtained 7:2, 7:1, 7:2, 6:2, 6:1 and 6:2 (Log of cfu/g), respectively. While, the result of survivability in simulated intestinal condition for (M1, A7), (M2, A7), (M3, A7), (M1, S2G), (M2, S2G) and (M3, S2G) was obtained as 6:2, 6:1, 6:2, 5:2, 5:1 and 5:2 (Log of cfu/g), respectively. Finally, there was a significant difference in the results of the monitoring of viable probiotic population during the shelf-life in different matrices at the examined temperatures.

In this study, the effect of different inoculum concentrations of E. faecium subsp. faecium strains on chemical, microbial and sensory properties of doogh was evaluated during two months of storage at 4 and 25°C. As compared with the control samples, samples containingstrain 1 of E. faecium subsp. faeciumand strain 2 of E. faeciumsubsp. faeciumat concentrations of 106 and 108 cfu/ml showed that decreasing of pH and increasing of acidity in the first month of storage.Also, inoculated samples of doogh with E. faecium subsp. faecium strains showed a significant decrease (p˂0.05) in the enumeration of molds and yeasts, coliform and mesophilic microorganisms at both storage temperatures (4 and 25°C). Among the samples, inoculated doogh sample with strains of E. faecium subsp. faecium with concentration of 108 cfu/ml was more effective in reducing the unwanted microbial load. Samples of inoculated doogh with concentration of 108 cfu/ml at 4 °C had an acceptable shelf life up to 50 days, while it was 40 days for the same control sample counterpart. Sensory evaluation showed that inoculated doogh samples were more acceptable than control doogh samples stored at 4°C. Generally, the E. faecium subsp. faecium strains, due to more decreasing of pH and higher acidification, reduced microbial load, and have a positive effect on sensory properties then can be used as a co-culture in the production of fermentation dairy products.

Probiotics are living microorganisms that have beneficial effects in the body and are used to stimulate the immune system and prevent many diseases in humans and animals. Diabetes is the most common endocrine disorder caused by a relative decrease or a complete lack of insulin, and in the long run it has extensive effects on most tissues in the body. The aim of this study was to evaluate the effect of Lactobacillus fermentum on diabetic rats. For this purpose, 32 rats were selected. The first group: non-diabetic control (n=8), the second group: diabetic control(n=8), the third group: diabetic rats treated with Lactobacillus fermentum (n=8), the fourth group: diabetes rats treated with glibenclamide (n=8). The findings showed that the group receiving Lactobacillus officinalis had a significant decrease (p <0.05) in glucose levels compared to the diabetic control group but, there was no significant increase in serum insulin levels. Also, the tissue sections of the pancreas showed that the bacteria had a recovery effect in the pancreatic tissue. Therefore, the results indicate that this bacterium can be used to reduce the complications and It can be considered in the treatment of diabetes.