Package of the Winter 2022

Background and objective:

Production of γ-aminobutyric acid has recently much interested because of its benefits for health. The objective of this study was to optimize γ-aminobutyric acid production by a novel identified Lactiplantibacillus pentosus isolated from a fermented shrimp paste of ruoc.

Material and Methods:

A species of lactic acid bacterial was isolated from ‘ruoc’, a high-salt fermented shrimp paste and identified using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. The γ-aminobutyric acid production was optimized using various culture conditions (initial cell density from 5 ´ 10⁵ to 5 ´ 10⁷ CFU ml^-1, monosodium glutamate concentration of 0.5-2% (w v^-1), initial pH of 4-9, incubation temperature of 30-50 °C and incubation time of 24-120 h) with one-factor-at-a-time approach.

Result and conclusion: Of 20 lactic acid bacteria isolated from ‘ruoc’, four isolates of R1, R3, R12 and R13 produced significant quantities of γ-aminobutyric acid. Isolate R13 produced the highest γ-aminobutyric acid quantity, identified as Lactiplantibacillus pentosus using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. A culture media optimization study was carried out for Lactiplantibacillus pentosus R13 to improve its γ-aminobutyric acid yield. Results showed that at optimal conditions of 1.5% monosodium glutamate (w v^-1), initial pH of 7, initial cell density of 5 ´ 10⁶ CFU ml^-1, cultivation temperature of 45 °C and fermentation time of 96 h, Lactiplantibacillus pentosus R13 produced 23.34 mM ±0.11 of γ-aminobutyric acid. In conclusion, γ-aminobutyric acid production by this isolate was verified to be heavily dependent on monosodium glutamate concentration, initial cell density, initial pH, incubation temperature and fermentation time.

 Background and Objective:

Resveratrol is a polyphenol with nutraceutical health benefits used as anticancer, antioxidant and anti-inflammatory with cardio protective effects. However, resveratrol lacks solubility and bioavailability and is affected by UV light, which decrease its use in food industries. It is possible to overcome these problems by loading resveratrol with appropriate biomaterials. Beta-lactoglobulin is known to form well-defined nanofibrils with various uses. The objective of this study was to use β-lg nanoscaled fibrils to increase bioavailability of resveratrol as well as preserving freshness and preventing enzymatic browning of sliced apples.

Material and Methods:

Novel composite nanofibrils were prepared by loading resveratrol on Beta-lactoglobulin nanofibrils using simple self-assembly method. Furthermore, atomic force microscopy, scanning electron microscopy, in-vitro release assay, weight loss, total acidity, total phenolic content and antioxidant activity studies were carried out to verify the biochemical sustainable release and bioavailability.

 Results and Conclusion:

Atomic force microscopy and scanning electron microscopy images showed the formation of well-defined composite nanofibrils with an average aspect ratio of 1000; as shown in other studies. In-vitro release assay revealed that resveratrol was successfully loaded on nanofibrils due to possible hydrogen bonding interactions and other non-covalent linkages. The highest encapsulation efficiency of 61.1% was achieved using low concentrations of resveratrol (10mg in 1ml), whereas encapsulation efficiency of 48.3% was achieved for high concentrations of resveratrol (20mg in 1ml). The assessed weight loss, total acidity, color, total phenolic content and antioxidant activities showed ~50% increases in the shelf-life and prevention of enzymatic browning due to improved bioavailability of resveratrol. The current study could successfully demonstrate antioxidant potency of resveratrol in sliced apples and help better protections against ageing. The formula can be used as a protective layer on high-value food products such as fruits susceptible to deteriorative conditions.

Background and Objective:

Ursolic acid is a pentacyclic triterpenoid with various biological characteristics. The objective of this study was to investigate potentially biological activities of ursolic acid extracted from apple peels.

Material and Methods:

Ursolic acid was extracted from apple peels and purified using column chromatography. Then, the biochemical was analyzed using ultraviolet-visible spectroscopy, high-performance thin-layer chromatography, Fourier-transform infrared spectroscopy and nuclear magnetic resonance techniques. Antimicrobial effects of the purified ursolic acid on pathogenic bacterial species of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Bacillus subtilis were assessed using minimum inhibitory concentration and disc diffusion methods. Furthermore, the biochemical radical scavenging ability was assessed using 1,1-diphenyl-1-picrylhydrazyl method. Wound healing characteristics of the purified ursolic acid was studied using scratch assay method.

Results and Conclusion:

Minimum inhibitory concentration and disc diffusion results verified antibacterial effects of ursolic acid on Gram-positive bacterial species. Ursolic acid at concentra-tions higher than 625 µg ml^-1 showed significant antioxidant activity, compared to that vitamin C did as reference antioxidant. It was shown that migration and proliferation of human umbilical vein endothelial cells can be promoted by the extracted ursolic acid, which was assessed via wound healing assays and 3(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide. Wound closure was 97%, revealed by the purified ursolic acid after 24 h. A low concentration of ursolic acid (< 20 µg ml^-1) stimulated proliferation of human umbilical vein endothelial cells; however, 100 µg ml^-1 of the extracted ursolic acid decreased the number of viable cells within 24 h (p < 0.05). Purified ursolic acid (10 µg ml^-1) was able to upregulate (almost two times) FLT1 and VEGF-A gene expression in human umbilical vein endothelial cells. Results suggest that ursolic acid is an effective antioxidant and includes excellent antibiotic characteristics. In addition, it can affect endothelial cell proliferation, which is significant to enhance angiogenesis and improve wound healing processes.

Background and Objective: Propionic acid bacteria are useful microorganisms that can produce beneficial food compounds. These bacteria mainly produce propionic acid that decrease the microbial population and growth along with increasing the shelf life. Propionibacterium freudenreichii was applied to produce propionic acid in yogurt in this study.

Material and Methods: First, the process variables like inoculum percentage, strain type, milk fat and inulin amount, fermentation temperature, sunflower oil quantity, and refrigerated duration on propionic acid production by Propionibacterium freudenreichii was evaluated using Plackett-Burman design as a screening method. Next the acid production was optimized by a central composite design with 3 major factors of seed size, concentration of inulin, and refrigerated storage.

Results and Conclusion: Analysis of variance showed that the models have been significant (p≤0.05). They represented that propionic acid production was influenced by three main factors. Optimized propionic acid production in yogurts by Propionibacterium freudenreichii ssp. shermanii (10⁸ CFU. ml^-1) was observed in 21 days after of refrigeration of skim-milk 2% (w v^-1), inulin (3% w v^-1) and incubation temperature of 43 °C. Reconfirmation test showed that the highest produced propionic acid was 12.53 ± 0.24 mg l^-1 in yogurt, which increased production up to 6.2 time. Results showed that Propionibacterium freudenreichii ssp. shermanii increases propionic acid contents in synbiotic yogurts containing inulin.

Background and Objective: Iranian drinking yogurt (Doogh) is one of the traditional beverages commercially produced and widely consumed. Mostly the spoilage of dairy products including Doogh is caused by a wide diversity of yeasts. In the present study, the swollen packages of pasteurized Doogh were investigated for yeast diversity and also the effect of predominant yeast on the proteins and peptides profiling of Doogh.

Material and Methods: The swollen packages of pasteurized Doogh were collected from a local dairy plant for one year. Isolation and identification were done using morphological, biochemical and molecular techniques. Afterward, the protein and peptide profiles of inoculated Doogh sample with high proteolytic activity yeast in comparison with Control sample were evaluated by SDS-PAGE and consequently MALDI-TOF-MS techniques.

Results and Conclusion: In total, 13 isolates belong to two genuse namely; Kluyveromyces and Candida were identified. According to 18S rRNA gene sequencing, the 8 isolates were identified as Kluyveromyces marxianus; 4 isolates matched with Kluyveromyces lactis, and 1 isolate was identified as Candida kefyr. Also, o-phthaldialdehyde test (OPA) showed that K. marxianus contain the highest proteolytic activity compare to other tested species. The results showed that the K. marxianus enzyme conducted protein profiles to β-lactoglubolin and α-lactalbumin isoforms and several peptides with molecular weight less than 10 KDa.

Background and Objective: Biodiesel is a well-known liquid fuel. However, a large quantity of glycerol is produced as a byproduct during the biodiesel production. If this is used as a substrate for value-added products such as monoacylglycerols, economic viability of the biodiesel process may improve. There are various uses of monoacylglycerol. However, its use as a substrate for oleogel is still a challenge. Therefore, the aim of this study was to assess the optimum acylglycerol production by immobilized lipase using glycerol from biodiesel processing and various plant oils as substrates. Moreover, use of acylglycerol for oleogel production was studied.

Material and Methods: First, glycerol was collected from biodiesel plants and purified using repeated cycles of acidification. Purified glycerol and various types of plant oils, including coconut, rice bran and palm oils, were used to produce acylglycerol via immobilized lipase catalysis. Then, acylglycerols from each plant oil were selected and used as substrates for oleogels. Acylglycerol was characterized following standard methods using gas chromatography-mass spectroscopy and Fourier transformed infrared spectroscopy. Moreover, structure and develop of oleogel were assessed using Fourier transformed infrared spectroscopy and scanning electron microscopy.

Results and Conclusion: The highest acylglycerol yield (91.15%) was achieved under conditions, including 20% enzyme loading, 6:1 glycerol to palm oil ratio, 8% water content, 40 °C reaction temperature and 24-h reaction time. Acylglycerol from glycerol with palm oil included mono, di and triacylglycerols with contents of 85.0, 10.0 and 2.0%, respectively. Results showed that types of oil included no effects on oleogel qualifications in this study and all oleogels included good characteristics use in foods.

Background and Aims:

Lentinus edodes (Shiitake) is a rich source of secondary metabolites, including exopolysaccharides. These compounds strengthen the immune system and play essential roles in prevention and treatment of several diseases, including cancers. A way to increase production of polysaccharides is the use of elicitors. Examples of these elicitors include microbial volatile organic compounds, which are produced in microo-rganism co-cultures. The objective of this study was to investigate effects of these compounds on production of Shiitake exopolysaccharides.

Materials and Methods:

To decrease cultivation time, Shiitake was cultured in four culture media, including (1) potato dextrose broth, (2) potato dextrose broth and D-glucose, (3) malt extract broth and (4) malt extract broth and D-glucose. After selecting appropriate culture media, fungal growth curve, kinetic growth of pellets and filamentous morphology were studied. Novel method of simultaneous aerial co-culture was used to increase production of Shiitake exopolysaccharides, which acted as an elicitor by inducing microbial volatile organic compounds of other microorganisms. Microbial volatile organic compounds were analyzed using gas chromatography-mass spectroscopy.

Results:

Malt extract medium containing glucose was selected for submerged and solid cultures of Shiitake and the growth time decreased to 18 d. Shiitake biomass production included 11 g.l^-1. Filamentous morphology included higher production rates due to higher surface-to-volume ratios, compared to that the pellet morphology did. Shiitake fungal biomass and exopolysaccharides in co-cultures with Aspergillus niger included 14 and 4 g.l^-1, respectively. Furthermore, biomass and exopolysaccharides included 11 and 4.7 g.l^{-1 in co-cultures with} Schizophyllum commune, respectively. Microbial volatile organic compounds produced by Aspergillus niger and Schizophyllum commune in co-cultures, as elicitors, increased biomass and exopolysaccharide productions in Shiitake. Therefore, it suggests that microorganism co-cultivation is a low-cost effective method for Shiitake exopolysaccharide production.