Applied Food Biotechnology
Volume:10 Issue: 3, Summer 2023

Yeasts are cheap and easily available sources of valuable bioactive compounds such as mannan. Spend yeasts as byproducts of various industries can be used to extract mannan, making the production process economical. Various factors such as growth conditions and cultivation system affect cell wall structure of the yeasts. The most common use of yeast mannan is as a prebiotic in animal feed. Its metabolism in the intestinal cell wall can produce postbiotic compounds such as short-chain fatty acids. Extraction of mannan has not been reported as a known classical method, depending on its final use and costs. The most popular cost-effective method is the acid-alkaline strategy. The current article has reviewed all aspects of structure, methods of extraction and recent studies on potential uses and bioactivities of yeast mannan and mannooligosaccharides, including modulation of animal gut microbiome, immune system and animal performance, as well as its antioxidant activity.

Literature review shows that mannan, manno-oligosaccharides, mannan rich fraction and their combination with probiotics and/or other bioactive compounds such as β-glucan may modulate compositions of gut microbiota. Various studies have shown that effectiveness of mannan depends on the species of animals and their age, diet, environmental conditions and rearing system. By optimizing the growth and cultivation conditions of yeasts, it is possible to increase proportions of mannan in the cell wall of yeasts, increasing efficiency of the industrial production. Although the most widely used yeast in industries is Saccharomyces cerevisiae, other Saccharomyces strains (e.g., Saccharomyces boulardii) and non-Saccharomyces yeasts (e.g., Pichia and Kluyveromyces spp.) can also be considered as high yielding strains.

The number of Muslims in Indonesia is increasing; hence, consumption of halal foods is increasing. This urges halal detection of foods as well. Direct qPCR is a method for DNA-based halal detection using crude DNA samples. One factor that affects the success of direct qPCR is the crude DNA. In this study, DNA extraction process was optimized by modifying the lysis step to achieve high-quality crude DNA, optimizing the qPCR conditions and validating the method.

Materials used for DNA extraction from meats and meat products included lysis buffer containing EDTA, NaCl, SDS, NaOH and tween-20. Materials used in qPCR assay included crude DNA, ddH20, primers and master mix. Genomes from meats and processed products were extracted using lysis buffer by optimizing lysis conditions (temperature and incubation time). The crude DNA was assayed for concentration and purity; then, results were compared to chloroform: isoamyl and the commercial methods. The DNA extract from lysis buffer was amplified using qPCR machine. Operational conditions such as DNA concentration, annealing temperature and primer concentration were optimized. Results were validated using specificity, repeatability, reproducibility, applicability, robustness and limit of detection assays.

Temperature for optimum lysis in extraction lysis buffer method included 75 °C for 25 min. Concentrations of DNA from the lysis buffer, chloroform-isoamyl and commercial methods did not significantly vary (p-value=0.094). The optimum conditions for qPCR method were set at DNA concentration of 50 ng μl-1, annealing temperature of 53 °C and primer concentration of 10 pmol. For the validation result, specificity assay showed that the method could be used to detect pork and wild boar in meats using ND4 primers. In addition, repeatability assay included 1.06% and reproducibility assay included 1.57%. Direct qPCR method can be used for various processed meat products and is resistant to inhibitors (alginate, calcium ions, EDTA and cellulose), except for polysaccharides. The LOD value achieved from the PCR sensitivity, linearity and efficiency assay were 0.001 ng μl-1, 0.996 and 110%, respectively. Results verify that the direct qPCR method is easy, fast, applicable, accurate and precise for the pork detection.

The proteolytic system of lactic acid bacteria hydrolyzes milk protein into several peptides, including those with antioxidative activities. The aim of this study was to assess antioxidant activities in cow and soy milks fermented by Lacticaseibacillus rhamnosus BD2, Lentilactobacillus kefiri YK4 and Lentilactobacillus kefiri JK17 previously isolated from kefir granules and their correlations with the peptide contents.

Reconstitutes of skimmed cow and soy milks were fermented by the highlighted isolates at 37 ℃ for 0, 24, 48 and 72 h. Fermented products were analyzed for the isolates, pH, total titratable acidity, antioxidant activity (% radical 2,2-diphenyl-1-picrylhydrazil inhibition and antioxidant capacity expressed in μg AAE.ml-1 whey) and total peptides. Fermented skimmed cow and soy milks with the highest antioxidant activity were then partially fractionated using molecular filters of 10 and 3 kDa. Fractions with the highest activity were analyzed further for peptide identification. Statistical analysis was carried out using one-way analysis of variance and Duncan multiple range tests (p≤0.05) using SPSS software v.16.0.

All isolates were able to grow in reconstituted skimmed cow and soy milks, while total count of reached to 9 log CFU.ml-1 with significant (p≤0.05) increases in titratable acidity and total peptides and decreased pH. Growth of the three isolates was mildly slower in soy milk than in skimmed cow milk. The maximum antioxidant activities were seen after 72-h fermentation of cow and soy milks. No differences were observed in antioxidant activity of cow milk fermented by the three isolates; however, Lacticaseibacillus rhamnosus BD2 produced the highest antioxidant activity in soy milk. In general, increases in antioxidant activities correlated with increases in the peptide contents. Fraction of less than 3 kDa of the two milks fermented by Lacticaseibacillus rhamnosus BD2 showed the highest antioxidant activity. Analyses of peptides present in these fractions using high resolution LC-MS/MS and in silico identification of peptides with antioxidant activity have been reported in this study. The present study suggests that the three isolates can be used as starter cultures in fermenting cow and soy milks to increase their antioxidant activities. Peptides with molecular weight of less than 3 kDa play key roles in antioxidant activity.

Lactic acid bacteria used in food processing for a long time are known for their benefits to consumers and their ability to produce natural antimicrobial compounds used as bio-preservatives in foods. The aim of the present study was the characterization and assessment of F21 strain, isolated from Lben (a traditional Moroccan fermented milk), as food biopreservative.

Isolate F21 was isolated from Lben, subjected to screening of inhibitory activity production, and identified based on morphological, biochemical and molecular identification. Then, the production and physicochemical characterization of the antagonistic substance were determined. Also, the safety profiling and biotechnological properties of isolate were evaluated. Finally, a biopreservative powder with antimicrobial activity was produced and assessed in various food systems (milk, ground beef and fresh cheese).

Of the isolated lactic acid bacteria, Enterococcus durans F21, isolated from Lben (a traditional Moroccan fermented milk), was remarkably endowed with interesting enterocin-like substance (heat stable and pH resistant) active against potentially pathogens and food spoilages (Listeria monocytogenes, Listeria innocua, Enterococcus faecalis, Brochothrix thermosphacta, and Mycobacterium smegmatis). Concerning the safety properties, Enterococcus durans F21 was not hemolytic, sensible to antibiotics tested, unable to produce biogenic amines and other virulence enzymes (gelatinase, DNase and urease). In addition, Enterococcus durans F21 showed satisfactory biotechnological characteristics such as acidification power, exopoly-saccharides production and antioxidant activity. The biopreservative powder containing enterocin-like substance F21 that was achieved via freeze-drying showed a minimum inhibition concentration of 60 AU ml-1 against Listeria monocytogenes in culture media. In addition, this biopreservative powder (at 665 AU ml-1) was able to improve safety and shelf-life of numerous foods (milk, Jben and ground beef). Thus, these results provided foundations for further uses of Enterococcus durans F21 as producer of potential food biopreservative agent.

Non-dairy probiotic beverages such as fruit juices have been popular for all age groups due to their vitamins, minerals, antioxidants and bioactive components with no allergens such as milk proteins and lactose. To exert their health benefits, probiotics should survive during food processing and storage as well as gastrointestinal tract. Incorporation of probiotics into fruit juices is more challenging than that in dairy products because of the low pH. Therefore, encapsulation of probiotics using various hydrocolloids and appropriate methods can protect probiotics from detrimental factors, improving their viability.

In the present study, free and encapsulated Lactiplantibacillus plantarum and Bifidobacterium bifidum were incorporated into apple juice and physicochemical characteristics of the fruit juice (pH, acidity, °Brix and color), viability of the probiotics and sensory evaluation of apple juices were investigated during 60-d storage at 4 °C.

Results showed encapsulation efficiencies of 90.21 and 85.54% for Lactiplantibacillus plantarum and Bifidobacterium bifidum in xanthan-chitosan hydrogels, respectively. Lactiplantibacillus plantarum and Bifidobacterium bifidum populations showed logarithmic decreases of 2.21 and 2.54 in free and 0.93 and 1.02 in encapsulated forms, respectively. However, the two bacteria survived in encapsulated form until the end of storage. In apple juices with free Lactiplantibacillus plantarum and Bifidobacterium bifidum, pH decreased from 3.7 to 3.11 and 3.3, respectively. In encapsulated probiotics, no significant differences were seen in pH of the samples. Moreover, apple juice samples with free probiotics included lower °Brix and higher acidity compared to the samples with encapsulated bacteria. Sensory evaluation of samples revealed that apple juices with encapsulated probiotics received higher scores than that apple juices with free bacteria did. The highest (3.95) and the lowest (2.48) overall acceptability scores after 60 d of storage were observed in samples containing encapsulated Bifidobacterium bifidum and free Lactiplantibacillus plantarum, respectively. It can be induced that use of xanthan-chitosan hydrogels can be used for the efficient encapsulation of probiotics and improve their survival during storage without adverse effects on sensory evaluation.