Recent developments on solid-state fermentation for production of microbial secondary metabolites: Challenges and solutions.

The existing health concerns for chemical additives entail natural preservation methods of food. The diversity of lactic acid bacteria (LAB) which can release a large panel of metabolites provide opportunities to utilize lactic acid fermentation (LAF) to serve the purpose. Some of released metabolites such as organic acids, alcohols, phenolics, exopolysaccharides, bacteriocins, and bioactive peptides and so on have been proved to exert antimicrobial and antioxidant activities. This directs for natural preservation of food along with potential health benefits. Further, LAF can also help in valorising food wastes through the release of bioactives and is an eco-friendly approach. To enhance the yield of bioactives, the utmost importance of modulating culture conditions, substrates and new strains has been emphasized. Specifically, this review summarises recently explored LAB genera involved in fermentation of foods or by-products, focusing on LAB antimicrobial and antioxidant metabolites and the recovery of such compounds upon fermentation in varied food systems. 

Lactic acid fermentation as a useful strategy to recover antimicrobial and antioxidant compounds from food and by-products

Novel peptides contribute to the antimicrobial activity of camel milk fermented with Lactobacillus plantarum IS10

Bioactive peptides used for food preservation can prolong the shelf life through bacteriostasis and antioxidation. On the one hand, bioactive peptides can inhibit lipid oxidation by scavenging free radicals, interacting with metal ions, and inhibiting lipid peroxidation. On the other hand, bioactive peptides can fundamentally inhibit the growth and reproduction of microorganisms by destroying their cell membranes or targeting intracellular components. Besides, bioactive peptides are biocompatible and biodegradable in vivo. Therefore, they are regarded as a promising alternative to chemical preservatives. However, bioactive peptides are easily affected by the external environment in practical application, which hinders their commercialization. Currently, the studies to overcome the weakness focus on encapsulation and chemical synthesis. Bioactive peptides have been applied to the preservation of various foods in experimental research, with good results. In the future, with the deepening understanding of their safety and structure-activity relationship, there may be more bioactive peptides as food preservatives.

Bioactive Peptides: A Promising Alternative to Chemical Preservatives for Food Preservation.

The development of convenient and accessible health-functional foods has become an area of increased interest in recent years. Probiotics, ginseng, and yogurts have been recognized as representative nutraceutical products. To improve the functionality of yogurts, co-fermentation was performed during yogurt preparation. Four kinds of yogurt were prepared using a combination of probiotic Lactobacillus brevis B7 and hydroponic ginseng based on plain yogurt. The fundamental characteristics of yogurts, including pH, titratable acidity, microbial counts, color, and physicochemical properties, were determined. To assess functionality, four different antioxidant assays and real-time PCR analysis using RAW 264.7 cells were performed. Finally, sensory evaluation was conducted to evaluate customer preference. Hydroponic ginseng supplementation influenced pH, solid content, lightness, and yellowness. However, probiotic supplementation did not affect most factors except pH. In functionality analysis, the yogurt co-fermented with probiotics and ginseng showed the highest antioxidant activity and gene expression levels of the immune-related factors TNF-α and iNOS in RAW 264.7 cells. Although ginseng supplementation received poor acceptance because of its color and flavor, these attempts were considered beneficial despite the risk. Overall, co-fermentation within a short yogurt preparation time presented the potential for improvement of functionality. These findings suggest a range of feasibility for the development of attractive nutraceutical products.

Co-Fermentation by Lactobacillus brevis B7 Improves the Antioxidant and Immunomodulatory Activities of Hydroponic Ginseng-Fortified Yogurt.

This study aimed at investigating the potential antifungal activity of low molecular weight peptides being a natural preservative generated from palm kernel cake (PKC) via solid state lacto-fermentation. Palm kernel cake was hydrolysed by L. casei generating a peptide mixture with a DH of 43.39% under predetermined optimum conditions of 5.6 days incubation, 3% glucose, and substrate/water ratio of 48/52 w/v. A total of 10 cationic peptides with molecular weight ranging from 932 to 1869 Da were identified by LC/MS-MS, in which 7 belonged to oil palm proteins and 3 de novo peptides biosynthesized by the microorganism during the fermentation process. The aqueous extract of the peptides mixture demonstrated strong antifungal activity against Aspergillus flavus (69.15%), Aspergillus niger (88.08%), Fusarium sp. (87.14%), and Penicillium sp. (71.84%). 1H-NMR spectroscopy results showed the presence of trace amounts of lactic and acetic acid, indicating that the antimicrobial activity was solely attributed by the low molecular weight peptides. The peptides mixture successfully delayed fungal growth, thus extending the shelf life of bread for up to 10 days when added to the bread at 2000 mg/kg. These findings indicated a promising application of the peptides mixture as a bio-preservative in extending the shelf life of bread.

Low molecular weight peptides generated from palm kernel cake via solid state lacto-fermentation extend the shelf life of bread

Date fruit (Phoenix dactylifera) have long history in food application due to the nutritional value, pleasant flavour and biological activity. This study aimed at investigating the antimicrobial ac...

Metabolomics profiling and antimicrobial activity of fermented date fruit (Khastawi) used as functional ingredients for making Asian confectionary (Dodol)

Nursyafiqah Mohamad Asri

Papers

Low molecular weight peptides generated from palm kernel cake via solid state lacto-fermentation extend the shelf life of bread

Metabolomics profiling and antimicrobial activity of fermented date fruit (Khastawi) used as functional ingredients for making Asian confectionary (Dodol)