نشریه کیفیت و ماندگاری تولیدات کشاورزی و مواد غذایی
پیاپی 1 (تابستان 1400)

The use of lactobacilli in the production of fermented foods has several thousand years old due to their ability to make the desired changes in the taste and texture of the food, as well as their importance in the human health. Different dairy products can be a source of new strains of Lactobacillus. Therefore, molecular identification and their genetic variation can be an effective step in identifying native lactobacilli reserves with specific functional characteristics and applying them to industrial dairy products. The purpose of this study is to isolate lactobacilli from flora in cow's milk of Narmeshir city and study their genetic diversity. For this purpose, 21 milk samples were collected from different regions of the city, and Lactobacilli wereisolated by the conventional phenotypic and biochemical methods. In order to screen and investigate the genetic diversity of isolated lactobacilli, five RAPD primers were randomly selected. After doing PCR, the analyses of genetic and phylogenetic diversity were performed using Pyelph software and phylogeny trees were drawn. Cluster analysis of molecular data was able to divide the isolates into seven distinct groups at a genetic distance of 10. K3 and K4 isolates were in group 1 and isolates K21, K13, and K11were in group 4. The remaining isolates were placed in separate groups. Since K3 and K4 isolates were from a region and K21 and K13 isolates were also collected from a region, their placement seems to be logical in a group.

There is a great consideration on the usage of biofertilizers as the alternative for chemical fertilizers. Some species of Enterobacter are described to be used in biofertilizers with direct and indirect plant growth promotion. This research aims to isolate phosphate solubilizing bacteria (PSB) and evaluate their effects on maize growth. So, rhizobacteria were isolated from the maize rhizosphere, and screening was performed on Sperber and Zinc oxide media. Other rhizobacterial traits such as ammonia and hydrogen cyanide production, nitrogen fixation, nitrate reduction, and the effect of environmental factors were also evaluated. Out of 42 PSB, 5 isolated strains with the best results were used for further tests and they were identified based on their 16S rRNA gene sequence as Enterobacter cloacae, Enterobacter hermoche, and Enterobacter sp. All selected strains were able to solubilize phosphate and zinc and could tolerate NaCl up to 7% and grow in pH 5 to 9, and finally, they could grow in temperatures in a range of 4 to 44oC. All 5 isolates could significantly increase shoot height and root length, and wet weight of shoot and root. Finally, according to the in-vitro and in-vivo results, the evaluated capabilities of bacterial strains isolated from maize are attractive and highlighted and it makes them good candidates for the construction of novel biofertilizers.

Listeria monocytogenes is a gram-positive bacterium that causes listeriosis in humans and animals and is present in most foods including dairy and milk. Listeria monocytogenes can cause abortion and mastitis in cattle. In humans, as well as infections in pregnant women, fetuses, and a newborn baby are seen as meningitis septicemia. Despite these microorganisms in milk can be considered as a health indicator. In this study, 50 samples of raw and unpasteurized milk in the city of Kerman were collected and transferred to the laboratory by observing the cold chain. The culture was performed on a Listeria-specific culture medium and phenotypic identification was performed. For molecular identification, the DNA of bacteria identified by the phenotypic method was extracted using a commercial kit. Listeria monocytogenes was detected by using a special IGF kit to identify this bacterium from the Iranian Gene Fanavaran Company. The PCR product was electrophoresed with 1% gel and specific bands were observed. The results showed that 30 and 27 samples of unpasteurized milk showed contamination against Listeria monocytogenes based on the methods performed, culture, and PCR, respectively. This shows the attention and observance of hygienic conditions during the production and preparation of milk and the necessity of using pasteurized milk.

Sourdough microflora generally contains yeast and lactic acid bacteria, and the interaction of microorganisms for its metabolic activity is important. Lactic acid bacteria produce numerous metabolites such as organic acids, enzymes, and exopolysaccharides during sourdough fermentation, which have a positive effect on the structure of the dough and bread's texture and staling. This study aimed to identify and compare the microbial flora of traditional bread dough in different cities of Kerman province by culture and molecular methods. MRS culture medium and Sabouraud Dextrose Agar were used in order to isolate lactic acid bacteria and yeasts respectively. Biochemical and antimicrobial tests were performed. 4 isolates of bacteria and 4 isolates of yeasts were identified by molecular method and comparing the resulting sequences of the sequences in the gene bank, respectively. Bacterial species were Weissella cibaria, Acinetobacter baumannii, Pediococcus pentosaceus, and Staphylococcus gallinarum, and yeasts Saccharomyces cerevisiae and Candida tropicalis. Based on the results, the microorganisms identified in this study can be suggested to improve the quality of bread and create a better taste and aroma of bread.

An experiment was conducted in order to investigate the effect of different levels of Thymus vulgaris powder (0, 1, 2, and 3%) on performance, egg quality, some ovarian parameters, and level of malondialdehyde in the liver and follicular fluid of Hy-Line w36 laying hens. The hens were divided into 4 equal treatment groups and each treatment consisted of 4 replicates in a completely randomized design. In the period of 26 to 33 weeks of age, no significant difference was observed among the dietary treatments in terms of egg production, shell-less egg ratio, feed intake, and feed conversion ratio; but egg weight and egg mass were affected by 2% thymus powder  (P<0.05). In the period of 34 to 39 weeks of age, shell-less eggs (%), egg production (%), and feed efficiency were not affected by thymus powder, but feed intake, egg mass, and egg weight were significantly affected by treatment 3 (P<0.05). The egg quality characteristics were measured at the end of weeks 26, 30, 34, and 38 of age. The results showed that only in week 26, the Haugh unit was significantly increased by 1 and 2% thymus powder (P<0.05). At the end of the experiment, the number of white, large yellow, and small yellow follicles, and level of malondialdehyde in the liver and follicular fluid were recorded and none of these were not affected by different levels of thymus powder. Overall, the experimental results showed that the use of 2% thyme powder in the laying hen diet improved the egg mass and egg weight, and also increased the Haugh unit during the peak production period.

In order to study the effect of different levels of soluble magnesium in irrigation water on growth characteristics of pistachio seedling, a greenhouse experiment was conducted as the split-plot form in the frame of completely random blocks design in Rafsanjan Pistachio Research Centre. For this purpose, two factors including pistachio base as the main factor at two levels (Zarand Badami and Ghazvini) and magnesium concentration in irrigation water at five levels (0, 0.5, 1, 2, and 3 mM magnesium derived from magnesium sulfate source) were applied. Before the application of treatments (at the end of week 8)and 6 months after the implementation of treatments, all growth characteristics of pistachio seedlings such as shoot height, initial and final diameter of seedling's shoot, total dry weight were measured. Results showed that the most length of seedling's shoot and the initial and final diameter of the seedling's shoot occur in the magnesium concentration of 0.5 and 1 mM. As the magnesium concentration increased to the highest level of 3 mM, the length of the seedling’s shoots and also the initial and final diameter of the seedling's shoot decreased by 1.44 cm, 0.16, and 0.22 mm, respectively. In both pistachio bases, the highest total dry weight was observed at concentrations of 0.5 and 1 mM magnesium. Total dry weight decreased with increasing magnesium concentration to 3 mM. The findings of this study made it clear that a concentration of 0.5 to 1 mM is the best concentration of magnesium in irrigation water for the optimal growth of two pistachio bases.

The Persian Gulf is the most important marine environment in the world. Because annually about 25000 oil tankers transfer in this Gulf and oil spill and pollution are so much in this area. The relationship between marine animals and degrading bacteria not well understand. The aim of this study is the characterization of symbiont crude oil-degrading bacteria in some Gastropods in the Persian Gulf. Gastropods were collected from five stations at the Persian Gulf. Symbiont crude oil-degrading bacteria were isolated from collected Gastropod by enrichment in ONR7a medium after 4 subcultures. The isolated bacteria were identified by biochemical and molecular methods. The effect of reducing the toxicity of heavy metals and the total amount of petroleum hydrocarbons on farmed fish and shrimp meat was investigated by decomposing bacteria. The degradation of crude oil was determined by spectrophotometry methods for each strain. In this study, 2 crude oil-degrading bacteria IAUK3585, IAUK3586 were isolated from Gastropod. The efficient strain that had the Thalassospira profundimaris and strain IAUK3586 the efficient strain that had the highest crude oil degradation belonged to genera. The results of reducing the toxicity of heavy metals and the total amount of petroleum hydrocarbons proved that the total amount of petroleum hydrocarbons and heavy metals in the pond with decomposing bacteria compared to the pond without decomposing bacteria and oil contamination and the pond without any These conditions were significantly reduced. This result proves that the decomposing bacteria that coexist with the abdomen have a significant effect on increasing the quality of fish and shrimp meat.