Microbial and physiochemical properties of Cheonggukjang fermented using Bacillus strains with antibacterial or antifungal activities

Current Perspectives on the Physiological Activities of Fermented Soybean-Derived Cheonggukjang

Cheonggukjang (CGJ, fermented soybean paste), a traditional Korean fermented dish, has recently emerged as a functional food that improves blood circulation and intestinal regulation. Considering that excessive consumption of refined salt is associated with increased incidence of gastric cancer, high blood pressure, and stroke in Koreans, consuming CGJ may be desirable, as it can be made without salt, unlike other pastes. Soybeans in CGJ are fermented by Bacillus strains (B. subtilis or B. licheniformis), Lactobacillus spp., Leuconostoc spp., and Enterococcus faecium, which weaken the activity of putrefactive bacteria in the intestines, act as antibacterial agents against pathogens, and facilitate the excretion of harmful substances. Studies on CGJ have either focused on improving product quality or evaluating the bioactive substances contained in CGJ. The fermentation process of CGJ results in the production of enzymes and various physiologically active substances that are not found in raw soybeans, including dietary fiber, phospholipids, isoflavones (e.g., genistein and daidzein), phenolic acids, saponins, trypsin inhibitors, and phytic acids. These components prevent atherosclerosis, oxidative stress-mediated heart disease and inflammation, obesity, diabetes, senile dementia, cancer (e.g., breast and lung), and osteoporosis. They have also been shown to have thrombolytic, blood pressure-lowering, lipid-lowering, antimutagenic, immunostimulatory, anti-allergic, antibacterial, anti-atopic dermatitis, anti-androgenetic alopecia, and anti-asthmatic activities, as well as skin improvement properties. In this review, we examined the physiological activities of CGJ and confirmed its potential as a functional food.

Antidiabetic, Anticholesterol, and Antioxidant Activity of Gryllusbimaculatus Fermented by Bacillus and Lactobacillus Strains

In this study, functionality of Gryllusbimaculatus (GB) fermented by Bacillus and Lactobacillus strain was investigated. GB was fermented by each of the following strains: probiotic Bacillus amyloliquefaciens MKSK-J1 (SKGB), probiotic Lactobacillus plantarum MKHA15 (HAGB), Bacillus amyloliquefaciens MKSE (SEGB), and Lactobacillus plantarum KCTC 3103 (LPGB). Fermentation was carried out at 35 °C for 24 h. In HAGB, complete inhibition of α-glucosidase and 3-hydroxy-methyl glutaryl-coenzyme A (HMG-CoA) reductase occurred (101.94% and 120.89%, respectively), and superoxide dismutase (SOD)-like activity (IC50) was significantly low (22.37 mg/mL). After in vitro digestion, SOD-like activity was the highest in HAGB (21.18%). In SKGB, reducing power (EC50) was significantly low (0.29 mg/mL). After in vitro digestion, the reducing was also highest in SKGB (86.06%). Fermentation enhanced the bioactivity of GB; in particular, MKHA15 was found to have great potential as a starter in the production of fermented GB, as it would offer multi-health functions, including antidiabetic, anticholesterol, and antioxidant activity.

Effects of Bacterial Fermentation on the Biochemical Constituents and Antioxidant Potential of Fermented and Unfermented Soybeans Using Probiotic Bacillus subtilis (KCTC 13241)

Fermented soybeans, cheonggukjang (CKJ), are considered to be more wholesome than soybeans in Korea. To select the best soybean cultivar for making functional CKJ, a comparison was made between the biological activities of four soybean cultivars in their unfermented soybean (UFS) and CKJ states. Changes in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays, superoxide dismutase (SOD)-like activity, total phenolic compounds, total amino acids, and isoflavones were investigated. The levels of DPPH, ABTS, SOD-like activity, and total phenolic compounds increased in CKJ among all cultivars. The isoflavone aglycone and total amino acids showed the highest amount in CKJ prepared from soybean cultivar Aga 3. These results suggest that the improved antioxidant activity of CKJ in all cultivars might occur because of the higher levels of aglycones and total phenolic compounds achieved during fermentation. Moreover, CKJ prepared from soybean cultivar Aga 3 showed higher antioxidant activity than the other cultivars and so can be considered for the commercial production of functional foods in the future.

Probiotic isolates from unconventional sources: a review

The use of probiotics for human and animal health is continuously increasing. The probiotics used in humans commonly come from dairy foods, whereas the sources of probiotics used in animals are often the animals’ own digestive tracts. Increasingly, probiotics from sources other than milk products are being selected for use in people who are lactose intolerant. These sources are non-dairy fermented foods and beverages, non-dairy and non-fermented foods such as fresh fruits and vegetables, feces of breast-fed infants and human breast milk. The probiotics that are used in both humans and animals are selected in stages; after the initial isolation of the appropriate culture medium, the probiotics must meet important qualifications, including being non-pathogenic acid and bile-tolerant strains that possess the ability to act against pathogens in the gastrointestinal tract and the safety-enhancing property of not being able to transfer any antibiotic resistance genes to other bacteria. The final stages of selection involve the accurate identification of the probiotic species.

Antimicrobial activity of Bacillus amyloliquefaciens EMD17 isolated from Cheonggukjang and potential use as a starter for fermented soy foods

A Bacillus strain with antimicrobial activity was isolated from Cheonggukjang and identified as Bacillus amyloliquefaciens. Filtered culture supernatants of B. amyloliquefaciens EMD17 strongly inhibited growth of Bacillus cereus ATCC14579, Listeria monocytogenes ATCC19111, and an ochratoxin (OTA) producing Penicillium spp. The antimicrobial activity was not decreased by heat, pH, and proteases treatment, indicating a non-proteinous nature of the antimicrobial substance. A B. amyloliquefaciens EMD17 culture added to a B. cereus ATCC14579 culture killed B. cereus cells completely in 6 h, showing the bacteriocidal effect. The srfAA gene encoding surfactin synthetase A was detected using PCR, indicating that surfactin might be the responsible agent. Genes encoding fengycin and iturin were also detected. MS indicated production of lipopeptides, including surfactin. Cheonggukjang and Doenjang were prepared using B. amyloliquefaciens EMD17 as a starter and growth of spiked B. cereus cells was completely inhibited.

Bacillus paralicheniformis sp. nov., isolated from fermented soybean paste

An isolate of a Gram-stain-positive, facultatively anaerobic, motile, rod-shaped, endospore-forming bacterium was recovered from soybean-based fermented paste. Phylogenetic analysis of the 16S rRNA gene indicated that the strain was most closely related to Bacillus sonorensis KCTC-13918T (99.5 % similarity) and Bacillus licheniformis DSM 13T (99.4 %). In phenotypic characterization, the novel strain was found to grow at 15–60 °C and to tolerate up to 10 % (w/v) NaCl. Furthermore, the strain grew in media with pH 6–11 (optimal growth at pH 7.0–8.0). The predominant cellular fatty acids were anteiso-C15 : 0 (37.7 %) and iso-C15 : 0 (31.5 %). The predominant isoprenoid quinone was menaquinone 7 (MK-7). The cell-wall peptidoglycan contained meso-diaminopimelic acid. A draft genome sequence of the strain was completed and used for phylogenetic analysis. Phylogenomic analysis of all published genomes of species in the B. licheniformis group revealed that strains belonging to B. licheniformis clustered into two distinct groups, with group 1 consisting of B. licheniformis DSM 13T and 11 other strains and group 2 consisting of KJ-16T and four other strains. The DNA G+C content of strain KJ-16T was 45.9 % (determined from the genome sequence). Strain KJ-16T and another strain from group 2 were subsequently characterized using a polyphasic taxonomic approach and compared with strains from group 1 and another closely related species of the genus Bacillus. Based upon the consensus of phylogenetic and phenotypic analyses, we conclude that this strain represents a novel species within the genus Bacillus, for which the name Bacillus paralicheniformis sp. nov. is proposed, with type strain KJ-16T ( = KACC 18426T = NRRL B-65293T).