Ochratoxigenic fungi in post-fermented tea and inhibitory activities of Bacillus spp. from post-fermented tea on ochratoxigenic fungi

Inhibitory Effect of Polypeptides Produced by Brevibacillus brevis on Ochratoxigenic Fungi in the Process of Pile-Fermentation of Post-Fermented Tea

“…B. brevis DTM05 (Accession: MG986217) was isolated from post-fermented tea samples, identified by the amplification sequence of 16S rRNA in a previous study [ 10 ] and preserved by our laboratory. A. carbonarius H9, also from a previous study [ 10 ], was used as the representative strain of OTA-producing fungus isolated from tea samples in the pile-fermentation process of post-fermented tea for subsequent anti-fungal experiments.…”

“…B. brevis DTM05 (Accession: MG986217) was isolated from post-fermented tea samples, identified by the amplification sequence of 16S rRNA in a previous study [ 10 ] and preserved by our laboratory. A. carbonarius H9, also from a previous study [ 10 ], was used as the representative strain of OTA-producing fungus isolated from tea samples in the pile-fermentation process of post-fermented tea for subsequent anti-fungal experiments. The preparation of A. carbonarius H9 spore suspension was as follows: A. carbonarius H9 were inoculated in potato dextrose agar medium (PDA) (potato, 200 g; glucose, 20 g; agar, 18 g and distilled water, 1 L) and cultured at 25 °C for 7 days.…”

“…In our previous study, six different species of Bacillus (B. substilis DTM01, B. coagulans DTM02, B. pumilus DTM04, B. brevis DTM05, B. licheniformis DTM06 and B. laterosporus DTM03) were able to inhibit the growth of ochratoxigenic fungi on the tea matrix during the first 7 days of pile-fermentation. Among those, B. brevis DTM05 was found to be the strain with the highest anti-fungal activity because it can produce antimicrobial polypeptides with a molecular weight ≤ 10 kDa [ 10 ], which is similar to the characteristics (molecular weight and anti-fungal properties) of peptide produced by B. brevis GM100 (named Bac-GM100 with a molecular weight of 4375.66 Da) reported by Ghadbane et al (2013) [ 22 ]. Although pure antimicrobial peptides have better antibacterial effects, they are limited in practical application due to their lower yields and higher costs.…”

“…A recent study by our research group reported that 100% of A. carbonarius strains, P. verrucosum strains and A. ochraceus strains, 8.33% of A. niger strains and 30% of A. tubingensis strains isolated from post-fermented tea have the ability to produce ochratoxin A (OTA). Among ochratoxigenic fungi, A. carbonarius was identified as one of the most powerful OTA-producers (OTA production reached 55.56 ± 4.64 ng/g in Czapek yeast extract agar (CYA), exceeding that of other ochratoxigenic fungi) [ 10 ] and it is often found in the pile-fermentation process of post-fermentation tea along with other ochratoxigenic fungi [ 11 ]. Ochratoxigenic fungi can grow normally and produce ochratoxin A at temperatures of 25~40 °C and relative humidity over 40% [ 12 , 13 ], which is consistent with the temperature and humidity conditions of pile-fermentation [ 14 ].…”

“…have potential anti-fungal ability (by producing antifungal enzymes, polypeptides or other metabolites) [ 16 , 17 , 18 ] and have been found to be widespread in post-fermented tea. Many Bacillus species such as B. subtilis , B. cereus , B. amyloliquefaciens , B. licheniformis , B. pumilus , B. brevis , B. coagulans and B. laterosporus , etc., have been isolated and identified in post-fermented tea [ 10 , 19 ]. B. subtilis AF1 can inhibit the growth of A. niger by destroying the cell wall of A. niger [ 20 ].…”