The Role of Enterococcus faecium as a Key Producer and Fermentation Condition as an Influencing Factor in Tyramine Accumulation in Cheonggukjang

Abstract

The study evaluated the role of Enterococcus faecium in tyramine production and its response to fermentation temperature in a traditional Korean fermented soybean paste, Cheonggukjang. Tyramine content was detected in retail Cheonggukjang products at high concentrations exceeding the recommended limit up to a factor of 14. All retail Cheonggukjang products contained Enterococcus spp. at concentrations of at least 6 Log CFU/g. Upon isolation of Enterococcus strains, approximately 93% (157 strains) produced tyramine at over 100 µg/mL. The strains that produced the highest concentrations of tyramine (301.14–315.29 μg/mL) were identified as E. faecium through 16S rRNA sequencing. The results indicate that E. faecium is one of the major contributing factors to high tyramine content in Cheonggukjang. During fermentation, tyramine content in Cheonggukjang groups co-inoculated with E. faecium strains was highest at 45 °C, followed by 37 °C and 25 °C. The tyramine content of most Cheonggukjang groups continually increased as fermentation progressed, except groups fermented at 25 °C. At 45 °C, the tyramine content occasionally exceeded the recommended limit within 3 days of fermentation. The results suggest that lowering fermentation temperature and shortening duration may reduce the tyramine content of Cheonggukjang, thereby reducing the safety risks that may arise when consuming food with high tyramine concentrations.

Tyrosinase Inhibitory Activity of Soybeans Fermented with Bacillus subtilis Capable of Producing a Phenolic Glycoside, Arbutin

“…The reduction in pH may be associated with the growth of total mesophilic viable bacteria during the fermentation of soybeans ( Figure 2 b). The bacterial counts of all soybean samples inoculated with B. subtilis strains (reference and isolated strains) dramatically increased from the initial 6 log CFU/g to over 9 log CFU/g on day 1 of fermentation and stayed constant thereafter, which is in agreement with previous studies on Cheonggukjang [ 43 , 44 ]. Mesophilic viable bacteria were not detected in the control throughout the incubation period.…”

“…As shown in Figure 2 a, the initial pH of all inoculated soybean samples (positive control and all experimental samples) and non-inoculated soybean samples (control) ranged from 6.17 to 6.22. The pH of the control remained constant during the incubation period (corresponding to the fermentation period), while those of all the inoculated soybean samples steadily decreased to ranges of 5.45 to 5.85 as fermentation progressed, which is in agreement with previous studies on Cheonggukjang fermentation [ 43 , 44 ]. The reduction in pH may be associated with the growth of total mesophilic viable bacteria during the fermentation of soybeans ( Figure 2 b).…”

“…The soybean fermentation experiments were conducted following the protocol described in previous studies [ 43 , 44 ]. White soybeans ( Glycine max Merrill) were purchased from a retail market in Sejong, Korea.…”

Structural Transformation and Creativity Induced by Biological Agents during Fermentation of Edible Nuts from Terminalia catappa

“…Syringol (6.03%), glutamine (1.71%), Methyl laurate (1.79%), Methyl palmitate (1.53%), palmitic acid (5.20%), palmitoleic acid (2.80%), and methyl oleate (2.97%) were the seven (7) major compounds detected in the unfermented extract. From this study, it could be inferred that these seven compounds ( Table 3 ) contributed to supporting growth of the probiotics facilitating the fermentation process [ 24 ]. Ten (10) major compounds, namely 2,3-butanediol (1.81%), butyric acid (16.20%), Propane-1,3-diol (19.66%), Neoheptanol (2.89%), 2-piperidinone (6.63%), Palmitoleic acid (1.18%), palmitic acid (4.19%), palmitoleic acid (1.48%), Formamide, N-(p-hydroxyphenethyl)- (2.80%), and cis-vaccenic acid (1.69%), were identified as the major metabolites in the fermented extract ( Table 4 ).…”

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

“…CGJ also enhances purine metabolism by increasing levels of uracil, thymine, xanthine, adenine, hypoxanthine, and guanine [ 43 , 176 ]. Recently, a culture platform based on Enterococcus faecium -derived CGJ with high accumulation of tyramine was shown to reduce the safety risks that may arise when consuming CGJ [ 162 , 177 , 178 ]. Heo et al [ 179 ] developed recQ as a genetic marker for the classification of Bacillus taxa.…”