The Biochemical Alteration of Enzymatically Hydrolysed and Spontaneously Fermented Oat Flour and Its Impact on Pathogenic Bacteria

Abstract

Avena sativa (A. sativa) oats have recently made a comeback as suitable alternative raw materials for dairy substitutes due to their functional properties. Amylolytic and cellulolytic enzyme-assisted modifications of oats produce new products that are more appealing to consumers. However, the biochemical and functional alteration of products and extracts requires careful selection of raw materials, enzyme cocktails, and technological aspects. This study compares the biochemical composition of different A. sativa enzyme-assisted water extracts and evaluates their microbial growth using spontaneous fermentation and the antimicrobial properties of the ferment extracts. Fibre content, total phenolic content, and antioxidant activity were evaluated using traditional methodologies. The degradation of A. sativa flour was captured using scanning electron microscopy (SEM); moreover, sugar and oligosaccharide alteration were identified using HPLC and HPLC-SEC after INFOGEST in vitro digestion (IVD). Additionally, taste differentiation was performed using an electronic tongue with principal component analysis. The oat liquid extracts were continuously fermented using two ancient fermentation starters, birch sap and Tibetan kefir grains. Both starters contain lactic acid bacteria (LAB), which has major potential for use in bio-preservation. In fermented extracts, antimicrobial properties against Gram-positive Staphylococcus aureus and group A streptococci as well as Gram-negative opportunistic bacteria such as Escherichia coli and Pseudomonas aeruginosa were also determined. SEM images confirmed the successful incorporation of enzymes into the oat flour. The results indicate that using enzyme-assisted extraction significantly increased TPC and antioxidant activity in both the extract and residues. Additionally, carbohydrates with a molecular mass (MM) of over 70,000 kDa were reduced to 7000 kDa and lower after the incorporation of amylolytic and cellulolytic enzymes. The MM impacted the variation in microbial fermentation, which demonstrated favourable antimicrobial properties. The results demonstrated promising applications for developing functional products and components using bioprocessing as an innovative tool.

Sustainable–Green Synthesis of Silver Nanoparticles Using Aqueous Hyssopus officinalis and Calendula officinalis Extracts and Their Antioxidant and Antibacterial Activities

“…Wells (Ø = 6 mm) were punched in the agar and filled with 50 µL of extracts. Agar plates were incubated at 37 • C for 24 h, and inhibition zones were measured and tabulated [37,57].…”

Optimization of Enzyme-Assisted Extraction of Bioactive Compounds from Sea Buckthorn (Hippophae rhamnoides L.) Leaves: Evaluation of Mixed-Culture Fermentation

“…The widely recognized yogurt starters, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus , are used in the fermentation of plant-based products [ 28 , 53 , 54 ]. In different studies, these strains have been found to alleviate the symptoms associated with lactose intolerance [ 55 ], which is related to the provision of β-galactosidase (lactase), a digestive enzyme that aids in breaking down lactose [ 56 , 57 ].…”

“…Following EAE, the liquid phase was used for further fermentation before freezing, as previously described by Streimikyte [ 28 ]. Specifically, 10% Tibetan Kefir grains was added to the liquid samples.…”

“…To assess the growth of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in spontaneously fermented samples with TKG, microbial evaluation was performed using agar diffusion [ 28 ]. Wells 6 mm in diameter were punched in the agar and filled with fermented extracts.…”

“…The best-known mixed-culture starters include Medusomyces gisevii pellicle, kefir grains, and birch sap, which implement bacterial and yeast symbiosis [ 25 ]. Although scientific investigations of mixed-culture starters are limited, the highest LAB content was identified for kefir grains, especially Tibetan kefir grains (TKG) [ 26 , 27 , 28 , 29 , 30 ].…”