Purification and identification of 1-deoxynojirimycin (DNJ) in okara fermented by Bacillus subtilis B2 from Chinese traditional food (Meitaoza)

Research Progress of α-Glucosidase Inhibitors Produced by Microorganisms and Their Applications

Based on the easy cultivation of microorganisms and their short cycle time, research on α-glucosidase inhibitors (α-GIs) of microbial origin is receiving extensive attention. Raw materials used in food production, such as cereals, dairy products, fruits, and vegetables, contain various bioactive components, like flavonoids, polyphenols, and alkaloids. Fermentation with specific bacterial strains enhances the nutritional value of these raw materials and enables the creation of hypoglycemic products rich in diverse active ingredients. Additionally, conventional food processing often results in significant byproduct generation, causing resource wastage and environmental issues. However, using bacterial strains to ferment these byproducts into α-GIs presents an innovative solution. This review describes the microbial-derived α-GIs that have been identified. Moreover, the production of α-GIs using industrial food raw materials and processing byproducts as a medium in fermentation is summarized. It is worth analyzing the selection of strains and raw materials, the separation and identification of key compounds, and fermentation broth research methods. Notably, the innovative ideas in this field are described as well. This review will provide theoretical guidance for the development of microbial-derived hypoglycemic foods.

α-Glucosidase Inhibitory Activity of Fermented Okara Broth Started with the Strain Bacillus amyloliquefaciens SY07

In this work, a new strain of Bacillus amyloliquefaciens SY07 isolated from a traditional fermented soybean food was reported to possess remarkable α-glucosidase inhibitor-producing ability. Different culture media were applied for the proliferation of B. amyloliquefaciens SY07, and it was found that fermented okara broth presented the highest α-glucosidase inhibitory activity, while Luria-Bertani medium showed a negative effect. The extract from fermented okara broth acted in a dose-dependent manner to inhibit α-glucosidase activity, with an IC50 value of 0.454 mg/mL, and main inhibitors in the fermentation extract presented a reversible, uncompetitive pattern according to Lineweaver-Burk plots. Moreover, 1-deoxynojirimycin, a recognized α-glucosidase inhibitor, was found in the extract. Results indicated that B. amyloliquefaciens SY07 could utilize okara, a by-product from the soy processing industry, to generate α-glucosidase inhibitors effectively, and be regarded as a novel excellent microbial candidate for safe, economical production of potential functional foods or ingredients with hypoglycemic effect.

Valorisation of By-Products from Soybean (Glycine max (L.) Merr.) Processing

In recent years, increased awareness of the health benefits associated with consuming soy-based foods, knowledge of milk-related allergies and a move towards more sustainable food production have led to an increase in the number of available soy-based products. The biggest producers in the world, the USA, South America and China, are from the Pacific region. This enormous production is accompanied by the accumulation of related by-products, in particular, a substance that is known as okara. Okara is a paste that is rich in fibre (50%), protein (25%), fat (10%), vitamins and trace elements. Its proper use would lead to economic advantages and a reduction in the potential for polluting the environment. Its high fibre content and low production costs mean that it could also be used as a dietary supplement to prevent diabetes, obesity and hyperlipidaemia. Chemical or enzymatic treatment, fermentation, extrusion, high pressure and micronisation can all increase the soluble fibre content, and thus improve nutritional quality and processing properties. However, the product also degrades rapidly due to its high moisture content (70-80%), which makes it difficult to handle and expensive to dry by conventional means. The aim of this paper is therefore to thoroughly study the existing literature on this subject in order to develop a general protocol for okara exploitation and valorisation. A cost/benefit analysis could drive the design of eco-friendly, sustainable protocols for the preparation of high-value nutritional products.

Anti-α-Glucosidase Activity by a Protease from Bacillus licheniformis

Anti-α-glucosidase (AAG) compounds have received great attention due to their potential use in treating diabetes. In this study, Bacillus licheniformis TKU004, an isolated bacterial strain from Taiwanese soil, produced AAG activity in the culture supernatant when squid pens were used as the sole carbon/nitrogen (C/N) source. The protein TKU004P, which was isolated from B. licheniformis TKU004, showed stronger AAG activity than acarbose, a commercial anti-diabetic drug (IC₅₀ = 0.1 mg/mL and 2.02 mg/mL, respectively). The molecular weight of TKU004P, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), was 29 kDa. High-performance liquid chromatography (HPLC) analysis showed that TKU004P may be a protease that demonstrates AAG activity by degrading yeast α-glucosidase. Among the four chitinous sources of C/N, TKU004P produced the highest AAG activity in the culture supernatant when shrimp head powder was used as the sole source (470.66 U/mL). For comparison, 16 proteases, were investigated for AAG activity but TKU004P produced the highest levels. Overall, the findings suggest that TKU004P could have applications in the biochemical and medicinal fields thanks to its ability to control the activity of α-glucosidase.

Conversion of Squid Pens to Chitosanases and Proteases via Paenibacillus sp. TKU042

Chitosanases and proteases have received much attention due to their wide range of applications. Four kinds of chitinous materials, squid pens, shrimp heads, demineralized shrimp shells and demineralized crab shells, were used as the sole carbon and nitrogen (C/N) source to produce chitosanases, proteases and α-glucosidase inhibitors (αGI) by four different strains of Paenibacillus. Chitosanase productivity was highest in the culture supernatants using squid pens as the sole C/N source. The maximum chitosanase activity of fermented squid pens (0.759 U/mL) was compared to that of fermented shrimp heads (0.397 U/mL), demineralized shrimp shells (0.201 U/mL) and demineralized crab shells (0.216 U/mL). A squid pen concentration of 0.5% was suitable for chitosanase, protease and αGI production via Paenibacillus sp. TKU042. Multi-purification, including ethanol precipitation and column chromatography of Macro-Prep High S as well as Macro-Prep DEAE (diethylaminoethyl), led to the isolation of Paenibacillus sp. TKU042 chitosanase and protease with molecular weights of 70 and 35 kDa, respectively. For comparison, 16 chitinolytic bacteria, including strains of Paenibacillus, were investigated for the production of chitinase, exochitinase, chitosanase, protease and αGI using two kinds of chitinous sources.

Reclamation of Marine Chitinous Materials for the Production of α-Glucosidase Inhibitors via Microbial Conversion

Six kinds of chitinous materials have been used as sole carbon/nitrogen (C/N) sources for producing α-glucosidase inhibitors (aGI) by Paenibacillus sp. TKU042. The aGI productivity was found to be highest in the culture supernatants using demineralized crab shell powder (deCSP) and demineralized shrimp shell powder (deSSP) as the C/N source. The half maximal inhibitory concentration (IC₅₀) and maximum aGI activity of fermented deCSP (38 µg/mL, 98%), deSSP (108 µg/mL, 89%), squid pen powder (SPP) (422 µg/mL, 98%), and shrimp head powder (SHP) (455 µg/mL, 92%) were compared with those of fermented nutrient broth (FNB) (81 µg/mL, 93%) and acarbose (1095 µg/mL, 74%), a commercial antidiabetic drug. The result of the protein/chitin ratio on aGI production showed that the optimal ratio was 0.2/1. Fermented deCSP showed lower IC₅₀ and higher maximum inhibitory activity than those of acarbose against rat intestinal α-glucosidase.

Utilization of Fishery Processing By-Product Squid Pens for α-Glucosidase Inhibitors Production by Paenibacillus sp

The supernatants (the solution part received after centrifugation) of squid pens fermented by four species of Paenibacillus showed potent inhibitory activity against α-glucosidases derived from yeast (79–98%) and rats (76–83%). The inhibition of acarbose—a commercial antidiabetic drug, used against yeast and rat α-glucosidases—was tested for comparison; it showed inhibitory activity of 64% and 88%, respectively. Other chitinolytic or proteolytic enzyme-producing bacterial strains were also used to ferment squid pens, but no inhibition activity was detected from the supernatants. Paenibacillus sp. TKU042, the most active α-glucosidase inhibitor (aGI)-producing strain, was selected to determine the optimal cultivation parameters. This bacterium achieved the highest aGI productivity (527 µg/mL) when 1% squid pens were used as the sole carbon/nitrogen source with a medium volume of 130 mL (initial pH 6.85) in a 250 mL flask (48% of air head space), at 30 °C for 3–4 d. The aGI productivity increased 3.1-fold after optimization of the culture conditions. Some valuable characteristics of Paenibacillus aGIs were also studied, including pH and thermal stability and specific inhibitory activity. These microbial aGIs showed efficient inhibition against α-glucosidases from rat, yeast, and bacteria, but weak inhibition against rice α-glucosidase with IC₅₀ values of 362, 252, 189, and 773 µg/mL, respectively. In particular, these aGIs showed highly stable activity over a large pH (2–13) and temperature range (40–100 °C). Various techniques, including: Diaoin, Octadecylsilane opened columns, and preparative HPLC coupled with testing bioactivity resulted in isolating a main active compound; this major inhibitor was identified as homogentisic acid (HGA). Notably, HGA was confirmed as a new inhibitor, a non-sugar-based aGI, and as possessing stronger activity than acarbose with IC_50, and maximum inhibition values of 220 μg/mL, 95%, and 1510 μg/mL, 65%, respectively. These results suggest that squid pens, an abundant and low-cost fishery processing by-product, constitute a viable source for the production of antidiabetic materials via fermentation by strains of Paenibacillus. This fermented product shows promising applications in diabetes or diabetes related to obesity treatment due to their stability, potent bioactivity, and efficient inhibition against mammalian enzymes.

Biosynthesis of α-Glucosidase Inhibitors by a Newly Isolated Bacterium, Paenibacillus sp. TKU042 and Its Effect on Reducing Plasma Glucose in a Mouse Model

Paenibacillus sp. TKU042, a bacterium isolated from Taiwanese soil, produced α-glucosidase inhibitors (aGIs) in the culture supernatant when commercial nutrient broth (NB) was used as the medium for fermentation. The supernatant of fermented NB (FNB) showed stronger inhibitory activities than acarbose, a commercial anti-diabetic drug. The IC50 and maximum α-glucosidase inhibitory activities (aGIA) of FNB and acarbose against α-glucosidase were 81 μg/mL, 92% and 1395 μg/mL, 63%, respectively. FNB was found to be strongly thermostable, retaining 95% of its relative activity, even after heating at 100 °C for 30 min. FNB was also stable at various pH values. Furthermore, FNB demonstrated antioxidant activity (IC50 = 2.23 mg/mL). In animal tests, FNB showed remarkable reductions in the plasma glucose of ICR (Institute of Cancer Research) mice at a concentration of 200 mg/kg. Combining FNB and acarbose enhanced the effect even more, with an added advantage of eliminating diarrhea. According to HPLC (High-performance liquid chromatography) fingerprinting, the Paenibacillus sp. TKU042 aGIs were not acarbose. All of the results suggest that Paenibacillus sp. TKU042 FNB could have potential use as a health food or to treat type 2 diabetes.

Use of Bacillus amyloliquefaciens HZ-12 for High-Level Production of the Blood Glucose Lowering Compound, 1-Deoxynojirimycin (DNJ), and Nutraceutical Enriched Soybeans via Fermentation

1-Deoxynojirimycin (DNJ) is an efficient α-glucosidase inhibitor (α-GI) with potential applications in the prevention and treatment of diabetes. In this study, 16 Bacillus strains were screened for α-GI rate, and the strain HZ-12 with the highest α-GI rate was identified as Bacillus amyloliquefaciens through the analysis of physiological biochemical characteristics and 16S rDNA sequence. By LC-MS/Q-TOF analysis, the α-GI component produced by B. amyloliquefaciens HZ-12 was identified as DNJ. Soybean was used as the substrate for the solid-state fermentation; 870 mg/kg DNJ was produced by B. amyloliquefaciens HZ-12 after optimizing the fermentation conditions and media, which was 3.83-fold higher than the initial yield. Also, evaluations of nutraceutical enrichment in the form of anticoagulant activity, antioxidant activity, total nitrogen (TN), and total reducing sugars (TRS) of the B. amyloliquefaciens HZ-12 fermented soybeans were substantially higher than unfermented soybeans. This study provided a promising strain for high-level production of DNJ and produced nutraceutical enriched soybeans by fermentation.

Improved 1-Deoxynojirimycin (DNJ) production in mulberry leaves fermented by microorganism

DNJ, an inhibitor of α-glucosidase, is used to suppress the elevation of postprandial hyperglycemia. In this study, we focus on screening an appropriate microorganism for performing fermentation to improve DNJ content in mulberry leaf. Results showed that Ganoderma lucidum was selected from 8 species and shown to be the most effective in improvement of DNJ production from mulberry leaves through fermentation. Based on single factor and three factor influence level tests by following the Plackett-Burman design, the optimum extraction yield was analyzed by response surface methodology (RSM). The extracted DNJ was determined by reverse-phase high performance liquid chromatograph equipped with fluorescence detector (HPLC-FD). The results of RSM showed that the optimal condition for mulberry fermentation was defined as pH 6.97, potassium nitrate content 0.81% and inoculums volume 2 mL. The extraction efficiency reached to 0.548% in maximum which is 2.74 fold of those in mulberry leaf.

Evolution of the Total Syntheses of Batzellasides the First Marine Piperidine Iminosugar

Batzellasides A-C are C-alkylated piperidine iminosugars isolated from a sponge Batzella sp. The first total synthesis of (+)-batzellaside B was achieved by employing a chiral pool approach starting from L-arabinose for the construction of a piperidine ring system. Subsequently a practical second-generation synthesis was developed by utilizing a Sharpless asymmetric dihydroxylation for the preparation of the common piperidine intermediate elaborated in the first-generation synthesis. The overall yield of batzellaside B was improved to 3.3% by introducing the exocyclic C8 stereocenter via facial selective hydride addition to a linear ketone. These syntheses allowed for the determination of the absolute stereochemistry of this natural product as well as for providing precious samples which would pave the way for further biological studies.

Isolation of the putative biosynthetic gene cluster of 1-deoxynojirimycin by Bacillus amyloliquefaciens 140N, its production and application to the fermentation of soybean paste

The 1-deoxynojirimycin (DNJ) biosynthetic gene cluster of Bacillus amyloliquefaciens 140N isolated from traditional Korean fermented food was isolated by PCR screening. It showed 78.9% inhibitory activity against α-glucosidase and produced 0.8 g/L of DNJ in an optimized medium containing 2% soluble starch, 1% tryptone, 0.05% KH(2)PO(4), and 0.05% (NH(2))(4)SO(4). Soybean paste fermented with B. amyloliquefaciens 140N produced DNJ with 84.4% inhibitory activity.

Production of the α-glycosidase inhibitor 1-deoxynojirimycin from Bacillus species

1-Deoxynojirimycin (DNJ), a potent α-glycosidase inhibitor, has therapeutic applications in treatments of HIV, Gaucher's disease, and diabetes. DNJ has been extracted from natural sources (mulberry leaves) for therapeutic purposes; however, DNJ ingredients are in limited supply and are costly to obtain on a large scale. Since certain strains of Bacillus and Streptomyces species reportedly produce DNJ, they may serve as potential sources for high-yield DNJ production. In this study, we obtained evidence for a DNJ production in Bacillus subtilis DSM704 by hydrophilic interaction chromatography-tandem mass spectrometry. In addition, from a screen of 750 microorganisms, we identified additional Bacillus strains (Bacillus amyloliquefaciens AS385 and Bacillus subtilis B4) that produce DNJ in large quantities. Investigation of the effect of various culture conditions, using Bacillus subtilis DSM704 and the DNJ high-production Bacillus strains, provided evidence for the importance of sorbitol supplementation on the yield of the DNJ precursor, 2-amino-2-deoxy-D-mannitol, thereby increasing DNJ production. The role of sorbitol in increased DNJ production was supported by an observed increase in mRNA expression of the biosynthetic gene, gabT1. When Bacillus amyloliquefaciens AS385 was cultured in medium supplemented with sorbitol, extracellular DNJ concentration reached a maximum of 460 mg/l of medium (equivalent to 9.20mg/g of freeze-dried medium), indicating that this strain can serve as a source for food- and drug-grade products. These findings not only lead to a further understanding of the DNJ biosynthetic pathway, but also suggest a method for microbial mass production of DNJ for therapeutic applications.