جستجوی مقالات مرتبط با کلیدواژه "پروتئین هیدرولیز شده کنجاله کنجد" در نشریات گروه "صنایع غذایی"

Protein hydrolysate is a valuable source of bioactive peptides. The production of protein hydrolysate through fermentation is an environmentally friendly approach preferred over enzymatic and chemical hydrolysis in most cases. This research employed Bacillus species, including Bacillus pumilus, Bacillus coagulans, Bacillus licheniformis, and Bacillus subtilis, to hydrolyze sesame meal protein. The investigated tests included measuring the concentration of peptides by the OPA method, DPPH radical inhibition, and iron ion reducing power, total antioxidant activity, and iron ion chelating activity. The concentration of peptides was evaluated after 24 h for Bacillus species. The lowest peptide concentration (0.656 mg/mL) was associated with the fermented treatment by B. licheniformis, while the highest value (1.38 mg/mL) was observed for the hydrolyzed treatment with B. subtilis. A significant difference (p<0.05) was observed among all the treatments. Results of DPPH radical inhibition showed the highest inhibition was associated with the samples hydrolyzed by B. coagulans (76.6%), and the lowest value was attributed to the hydrolysate by B. licheniformis (57.36%). The sample fermented with B. pumilus exhibited higher reducing power (0.992 absorbance at 700 nm) with a significant difference (p<0.05) observed between the treatments. The highest chelating activity (85.6%) was observed in the sample fermented with B. subtilis. The total antioxidant activity demonstrated that the protein hydrolysate with fermentation by B. coagulans had the highest absorbance value at 695 nm with a significant difference between the treatments (p<0.05). In conclusion, the fermentation of sesame meal protein by Bacillus species resulted in the production of protein hydrolysate with substantial antioxidant activity, positioning it as a promising source for inclusion in food formulations.

Nowadays, antibiotic resistance is increasing in all parts of the world and is emerging and expanding globally. Due to their natural antimicrobial properties and low tendency to develop bacterial resistance, antimicrobial peptides can be a good candidate as an alternative to synthetic antibiotics. Bioactive peptides are produced using enzymatic hydrolysis by enzymes extracted from microorganisms and plants, digestive enzymes, and fermentation by proteolytic starter cultures. Enzymatic hydrolysis of proteins is performed by commercial proteases or a combination of several proteolytic enzymes. Commercial proteases are expensive due to their specificity. Among the strategies for protein hydrolysis with the aim of obtaining bioactive peptides is microbial fermentation, which is more environmentally friendly and has a high potential for use in industry due to its relatively low cost compared to commercial enzymes. It is a suitable method for the hydrolysis of sesame meal protein. Bacillus species are bacteria that have high proteolytic activity and are able to produce different endopeptidases in the fermentation medium. The activity of endopeptidases in the environment containing proteins causes the production of peptides with small sizes and free amino acids in higher amounts compared to enzymatic hydrolysis, which is one of the advantages of using Bacillus species with high proteolytic activity compared to pure enzymes. In general, the purpose of this research was to produce sesame meal protein hydrolysate by fermentation with Bacillus subtilis and to investigate its antimicrobial and antioxidant activity.

In this study, at the first step, sesame meal was defatted with hexane at a ratio of 1:5, then it was dried and sesame meal protein isolate was extracted, and the optimization of fermentation conditions was determined by the response surface methodology (RSM). Independent variables, including temperature (30 to 45 ˚C), time (12 to 36 h), and substrate concentration (2 to 6%), were considered. The antioxidant properties of the treatments, including DPPH radical scavenging activity, ferric ion reducing power, and antimicrobial activity, were investigated, and the optimum treatment was selected. Then the protein hydrolysate was freez-dried and stored at -20 °C.

According to the results, temperature (39.68 °C), time (30.07 h), and substrate concentration (4.85%) were selected as optimum conditions. Under these conditions, DPPH radical scavenging activity and ferric ion reducing power of hydrolysate were 63.57% and 0.9951 (absorbance at 700 nm), respectively. The inhibition percentages of Staphylococcus aureus (59.58%), Escherichia coli (6.55%), Listeria monocytogenes (62.43%), and Clostridium perfringens (50.97%) were obtained in the optimized condition. Bacillus subtilis, in the presence of sesame meal protein, showed significant (p<0.05) protease activity over time. After 48 hours, the clear zone diameter was determined to be 22 mm. The clear zone created by this strain showed that Bacillus subtilis has high proteolytic activity and can be a suitable bacterium for hydrolyzing sesame meal protein with the aim of obtaining hydrolysates with the highest antimicrobial and antioxidant activities. The antimicrobial activity of the protein hydrolysate can be due to the higher degree of hydrolysis. By increasing the hydrolysis time, peptides with low molecular weight are produced, which cause better interaction with the microbial cell membrane, disrupt the membrane, and lead to the inhibition of the microorganism. According to the results, the sesame meal protein hydrolysate showed more inhibitory effect against gram-positive bacteria than gram-negative bacteria (Escherichia coli). Researchers reported that the difference in sensitivity to antimicrobial compounds between gram-positive and gram-negative bacteria can be attributed to the structure and composition of the cell envelope (cytoplasmic membrane or outer membrane, and cell wall). In general, the bioactivity properties of protein hydrolysate depend on the amino acid composition, sequence, and molecular weight of the amino acids. The antioxidant activity can be due to the high content of polar and aromatic amino acids. By further hydrolysis of proteins, peptides and polar free amino acids are produced that interact with free radicals and converted into safe and stable intermediate products.

In this study, Bacillus subtilis strain was used to ferment sesame meal protein, which is a rich source of protein, to produce protein hydrolysate with maximum antimicrobial and antioxidant activities. Results showed that the protein hydrolysate obtained from sesame meal protein isolate had antimicrobial and antioxidant activities. It can be used as a natural antimicrobial or antioxidant agent in the formulation of food or pharmaceutical industry to improve the health of society.