Effect of filamentous fungi fermentation on the extractability and physicochemical properties of β-glucan in oat bran

Effects of Ganoderma lucidum fermentation on the structure of Tartary buckwheat polysaccharide and its impact on gut microbiota composition

Fermentation modifies plant polysaccharides and enhances their bioactivity. In this study, polysaccharides were extracted from Ganoderma lucidum-fermented (FBP) and non-fermented (NBP) Tartary buckwheat. The structure of the polysaccharides and their effects on gut microbial composition were explored. According to the results, the molecular weight of FBP lowered from 8.86 × 105 Da to 3.83 × 104 Da, the fermentation process produced fucose (7.72 %) and mannose (6.68 %), and the content of glucose and galactose increased. Compared with NBP, FBP showed a significant increase in solubility, crystallinity and thermal stability, while there was a decrease in apparent viscosity. The in vitro fecal fermentation results suggested that FBP promoted the production of short-chain fatty acids, with acetic acid, propionic acid and butyric acid being the main metabolites. FBP and NBP dramatically decreased the relative abundance of Escherichia-Shigella. FBP increased the relative abundances of Bacteroides, Parabacteroides, and Megamonas, while NBP increased those of Bifidobacterium and Phascolarctobacterium. Finally, further analysis of functional prediction indicated that carbohydrate metabolism, lipid metabolism and cardiovascular disease were the most vital pathways for FBP to promote health. This study offers some theoretical foundation for the chemical structure and regulation of gut microbiota by Ganoderma lucidum fermented buckwheat modified polysaccharides.

Integration of ultrasound and microwave pretreatments with solid-state fermentation enhances the release of sugars, organic acids, and phenolic compounds in wheat bran

Wheat bran (WB), a byproduct of milling, is rich in bioactive compounds with significant health benefits. This study aimed to enhance the release of phenolic compounds, sugars, and organic acids from WB by integrating ultrasound (UsP) and microwave (MWP) pretreatments with solid-state fermentation (SSF). UsP and MWP disrupted WB cell walls, followed by SSF with Aspergillus niger. UsP increased total phenolic content by 21.30 % on day 1 of SSF. UsP and MWP boosted the availability of bound phenolic compounds like vanillic acid and dihydroxybenzoic acid. Both pretreatments enhanced antioxidant activity compared to untreated fermented WB, with peak activity on day 5 of fermentation at 1411 ± 5.156 μM Trolox/100 g DW for UsP WB and 291.6 ± 1.092 μM Trolox/100 g DW for MWP WB. This integrated approach improved the extraction efficiency of fermentable monosaccharides, particularly glucose and xylose, offering a sustainable bioprocessing strategy for WB valorization and supporting the circular bioeconomy.

New insights into adlay seed bran polysaccharides: Effects of enzyme-assisted Aspergillus niger solid-state fermentation on its structural features, simulated gastrointestinal digestion, and prebiotic activity

Adlay seed bran, typically discarded or used as animal feed, represents a significant resource waste. This study investigates the structural and physicochemical properties, in vitro digestive behavior, and fecal fermentation profiles of adlay seed bran polysaccharides (ASBPs) prepared using different methods. These methods include hot water extraction, Aspergillus niger solid-state fermentation (SSF), and enzyme-assisted SSF with β-glucosidase, cellulase, and xylanase, referred to as ASBP, ASBP-F, ASBP-GF, ASBP-CF, and ASBP-XF, respectively. Results showed that enzyme-assisted SSF with A. niger improved extraction efficiency and uniformity of ASBPs, increasing total neutral sugars, uronic acids, mannose, and galactose while reducing glucose content, molecular weight, and particle size. ASBP-CF had the best extraction rate, sugar content, lowest molecular weight, finest uniformity, and smallest particle size. In simulated digestion tests, all ASBP variants were stable in stomach and small intestine conditions but degradable by human fecal microbiota, showing varying fermentability levels. ASBPs increased Bacteroidetes populations, inhibited Proteobacteria growth, and enhanced short-chain fatty acid (SCFAs) production, with ASBP-CF showing the highest fermentability and prebiotic efficacy. ASBP-CF was particularly effective in promoting beneficial bacteria like Bacteroides and restraining harmful bacteria such as Escherichia_Shigella, producing more SCFAs during fermentation. These findings suggest that ASBP-CF has potential as a dietary supplement to improve gut health, presenting a high-value utilization strategy for adlay seed bran.

Enhancing phenolic and lipid compound production in oat bran via acid pretreatment and solid-state fermentation with Aspergillus niger

Oat (Avena sativa) processing generates a large amount of by-products, especially oat bran. These by-products are excellent sources of bioactive compounds such as polyphenols and essential fatty acids. Therefore, enhancing the extraction of these bioactive substances and incorporating them into the human diet is critical. This study investigates the effect of acid pretreatment on the solid-state fermentation of oat bran with Aspergillus niger, with an emphasis on the bioaccessibility of phenolic acids and lipid profile. The results showed a considerable increase in reducing sugars following acid pretreatment. On the sixth day, there was a notable increase in the total phenolic content, reaching 58.114 ± 0.09 mg GAE/g DW, and the vanillic acid level significantly rose to 77.419 ± 0.27 μg/g DW. The lipid profile study revealed changes ranging from 4.66 % in the control to 7.33 % on the sixth day of SSF. Aside from biochemical alterations, antioxidant activity measurement using the DPPH technique demonstrated the maximum scavenging activity on day 4 (83.33 %). This study highlights acid pretreatment's role in enhancing bioactive compound accessibility in solid-state fermentation and its importance for functional food development.

Cereal dietary fiber regulates the quality of whole grain products: Interaction between composition, modification and processing adaptability

The coarse texture and difficulty in processing dietary fiber (DF) in cereal bran have become limiting factors for the development of the whole cereal grain (WCG) food industry. To promote the development of the WCG industry, this review comprehensively summarizes the various forms and structures of cereal DF, including key features such as molecular weight, chain structure, and substitution groups. Different modification methods for changing the chemical structure of DF and their effects on the modification methods on physicochemical properties and biological activities of DF are discussed systematically. Furthermore, the review focusses on exploring the interactions between DF and dough components and discusses the effects on the gluten network structure, starch gelatinization and retrogradation, fermentation, glass transition, gelation, and rheological and crystalline characteristics of dough. Additionally, opportunities and challenges regarding the further development of DF for the flour products are also reviewed. The objective of this review is to establish a comprehensive foundation for the precise modification of cereal DF, particularly focusing on its application in dough-related products, and to advance the development and production of WCG products.

Recent advances in polysaccharide biomodification by microbial fermentation: production, properties, bioactivities, and mechanisms

Polysaccharides are natural chemical compounds that are extensively employed in the food and pharmaceutical industries. They exhibit a wide range of physical and biological properties. These properties are commonly improved by using chemical and physical methods. However, with the advancement of biotechnology and increased demand for green, clean, and safe products, polysaccharide modification via microbial fermentation has gained importance in improving their physicochemical and biological activities. The physicochemical and structural characteristics, biological activity, and modification mechanisms of microbially fermented polysaccharides were reviewed and summarized in this study. Polysaccharide modifications were categorized and discussed in terms of strains and fermentation techniques. The effects of microbial fermentation on the physicochemical characteristics of polysaccharides were highlighted. The impact of modification of polysaccharides on their antioxidant, immune, hypoglycemic, and other activities, as well as probiotic digestive enhancement, were also discussed. Finally, we investigated a potential enzyme-based process for polysaccharide modification via microbial fermentation. Modification of polysaccharides via microbial fermentation has significant value and application potential.

Growing of fungi on the stored low denatured defatted soybean meals and the hydrolysis of proteins and isoflavone glycosides by fungal enzymes

Recently, more and more attention has been paid to the effects of fungal contamination and fungal enzymes secreted in raw grain on product quality. As the starting material of protein and active components, the quality of low denatured defatted soybean meals (LDSM) directly determines the qualities of subsequent products. In previous studies, we have revealed that infection with Aspergillus ochraceus protease causes significant hydrolysis of proteins. In this study, growing of fungi on the stored low denatured defatted soybean meals (LDSM) was analyzed by high-throughput sequencing and real-time PCR, which revealed that the abundance of Aspergillus increased significantly after storage. Twenty fungal proteases and 9 fungal glucosidases were found in stored LDSM and zymography showed that the proteases were of serine-type with some cysteine and aspartic activities. Proteolysis of the soybean storage proteins mainly occurred after the hydration of LDSM and the average molecular weight of soy proteins decreased from 57.9 kDa to 30.7 kDa after 60 min's of hydrolysis. Two-dimensional electrophoresis (2-DE) analysis found the polypeptide fragments from soybean 7S and 11S proteins with molecular weight around 10-25 kDa in the hydrated LDSM. Glycosylated isoflavones were hydrolyzed in both dry and hydrated stored LDSM which resulted in significant (p < 0.05) increase in the contents of isoflavone aglycones. This study suggested that fungi contamination be a new factor affecting the properties of LDSM derived soy protein products.

Upgrading the accumulation of ginsenoside Rd in Panax notoginseng by a novel glycosidase-producing endophytic fungus G11-7

A novel endophytic fungus producing beta-glucosidase was isolated and characterized from pigeon pea (Cajanus cajan [L.] Millsp.), which has excellent properties in converting ginsenoside Rb1 to ginsenoside Rd in Panax notoginseng. According to the 16S rDNA gene sequence, the G11-7 strain was identified as Fusarium proliferatum, and the accession number KY303906 was confirmed in GenBank. The G11-7 immobilized spores, in which the activity of beta-glucosidase could reach 0.95 U/mL, were co-cultured with P. notoginseng plant material to obtain a continuous beta-glucosidase supply for the biotransformation of ginsenoside Rb1 to Rd. Under the liquid-solid ratio (20:1), initial pH (6.0), and temperature (30 °C) constituents, the maximum ginsenoside Rd yield was obtained as 9.15 ± 0.65 mg/g, which was 3.67-fold higher than that without fungal spore co-culture (2.49 ± 0.98 mg/g). Furthermore, immobilized G11-7 spores showed significant beta-glucosidase producing ability which could be recovered and reused for 6 cycles. Overall, these results suggested that immobilized G11-7 offered a promising and effective approach to enhance the production of ginsenoside Rd for possible nutraceutical and pharmaceutical uses.

Novel processing strategies to enhance the bioaccessibility and bioavailability of functional components in wheat bran

Dietary fiber, polysaccharides and phenols are the representative functional components in wheat bran, which have important nutritional properties and pharmacological effects. However, the most functional components in wheat bran exist in bound form with low bioaccessibility. This paper reviews these functional components, analyzes modification methods, and focuses on novel solid-state fermentation (SSF) strategies in the release of functional components. Mining efficient microbial resources from traditional fermented foods, exploring the law of material exchange between cell populations, and building a stable self-regulation co-culture system are expected to strengthen the SSF process. In addition, emerging biotechnology such as synthetic biology and genome editing are used to transform the mixed fermentation system. Furthermore, combined with the emerging physical-field pretreatment coupled with SSF strategies applied to the modification of wheat bran, which provides a theoretical basis for the high-value utilization of wheat bran and the development of related functional foods and drugs.

Insight into the protein degradation during the broad bean fermentation process

Broad bean fermentation is of vital importance in PixianDouban (PXDB) production, as well as a key process for microorganisms to degrade protein, which lays the foundation for the formation of PXDB flavor. In this study, two fungi and bacteria were screened, and their morphology, molecular biology, growth, and enzyme production characteristics were analyzed, and then they were applied to the broad bean fermentation simulation system. The protein, peptide, amino acid, amino nitrogen, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in the system were evaluated. The results showed that the four microorganisms were Aspergillus oryzae, Aspergillus jensenii, Staphylococcus gallinarum, and Enterobacter hormaeche. Aspergillus oryzae had the highest protease activity at pH 7.0, while the other three strains had better enzyme activity stability under neutral acidic conditions. And the total protein (F1 and F2 were 18.32 g/100 g, 19.15 g/100 g, respectively), peptides (11.79 ± 0.04 mg/g and 12.06 ± 0.04 mg/g), and amino acids (55.12 ± 2.78 mg/g and 54.11 ± 1.97 mg/g) of the fungus experimental groups (F) were higher than the bacterial experimental groups (B). In addition, the enzyme system produced by fungi exhibited a stronger ability for albumin (20 kDa) and glutenin (<30 kDa) deterioration in neutral conditions, while the bacterial enzyme system was more efficient in degrading albumin (<30 kDa) and glutenin (20-30 kDa) in acidic conditions, as indicated by SDS-PAGE. These findings showed that both bacteria and fungi played an important role in the degradation of protein in different fermentation stages of broad bean fermentation.

Practical applications

There is a lack of comprehensive understanding of the protein composition and protein degradation mechanism of broad beans in the fermentation stage of PXDB. This research work explored the differences in the degradation of PXDB fermented protein by different microorganisms, and provided a theoretical basis for optimizing the production of PXDB and improving the quality of PXDB.

Comparison of distribution and physicochemical properties of β-glucan extracted from different fractions of highland barley grains

Highland barley grains were roller-milled to produce five different fractions (B-1, B-2, B-3, B-4, and B-5). The distribution and physicochemical properties of β-glucans from five roller-milled fractions were investigated. The B-4 fraction contained the highest concentration of β-glucan (4.40%), and the outermost bran (B-1) had the lowest β-glucan content (1.01%). Besides, β-glucans from inner core B-5 (BG-5) had higher M_w (6.482 × 10⁵ g/mol), whereas β-glucans from outer bran B-1 (BG-1) showed lower M_w (5.859 × 10⁴ g/mol) than those from other fractions. Accordingly, the viscosity of BG-5 was highest (0.038-0.365 Pa·s), and the water solubility index of BG-1 was highest (50.43-90.71%). BG-5 showed stronger foam stability and emulsifying properties but weaker foaming capability, while BG-1 exhibited stronger foaming capability. The foaming capability and emulsifying properties of β-glucan samples were better under the neutral condition (pH = 7). The foam capabilities of all β-glucan samples displayed higher values at 65 °C, and emulsifying properties exhibited higher values at 45 °C. This study is expected to promote the application of highland barley β-glucans in food industry.

Comparison of physicochemical properties of β-glucans extracted from hull-less barley bran by different methods

In this study, four extraction methods, including ultrasonic extraction (UE), hot water extraction (HWE), microwave extraction (ME), and microwave-assisted ultrasonic extraction (MUE) were utilized to extract β-glucan from hull-less barley bran. Extraction yields and physicochemical properties of β-glucans extracted by different methods were investigated. The MUE displayed a highest extraction yield (2.16%) within shorter extraction time. Besides, β-glucans extracted by MUE (MUE-G) had higher number-average molecular weight (M_n) (3.415 × 10⁵), whereas β-glucans extracted by UE (UE-G) showed lower M_n (2.257 × 10⁵) as compared to other methods. Accordingly, apparent viscosity of MUE-G was highest, while water solubility index of UE-G was highest (34.18-88.81%) at tested temperature ranges (25-95 °C). The MUE-G shower stronger foam stability and emulsifying properties and weaker foaming capability, while UE-G exhibited stronger foaming capability. The foaming capability and emulsifying properties of β-glucan products were better in neutral solutions (pH = 7) than in the acidic (pH = 4) and alkaline (pH = 9).