Enhanced cercosporin production by co-culturing Cercospora sp. JNU001 with leaf-spot-disease-related endophytic bacteria

Abstract

Background Owing to the excellent properties of photosensitization, cercosporin, one of naturally occurring perylenequinonoid pigments, has been widely used in photodynamic therapy, or as an antimicrobial agent and an organophotocatalyst. However, because of low efficiency of total chemical synthesis and low yield of current microbial fermentation, the limited production restricts its broad applications. Thus, the strategies to improve the production of cercosporin were highly desired. Besides traditional optimization methods, here we screened leaf-spot-disease-related endophytic bacteria to co-culture with our previous identified Cercospora sp. JNU001 to increase cercosporin production. Results Bacillus velezensis B04 and Lysinibacillus sp. B15 isolated from leaves with leaf spot diseases were found to facilitate cercosporin secretion into the broth and then enhance the production of cercosporin. After 4 days of co-culture, Bacillus velezensis B04 allowed to increase the production of cercosporin from 128.2 mg/L to 984.4 mg/L, which was 7.68-fold of the previously reported one. Lysinibacillus sp. B15 could also enhance the production of cercosporin with a yield of 626.3 mg/L, which was 4.89-fold higher than the starting condition. More importantly, we found that bacteria B04 and B15 employed two different mechanisms to improve the production of cercosporin, in which B04 facilitated cercosporin secretion into the broth by loosening and damaging the hyphae surface of Cercospora sp. JNU001 while B15 could adsorb cercosporin to improve its secretion. Conclusions We here established a novel and effective co-culture method to improve the production of cercosporin by increasing its secretion ability from Cercospora sp. JNU001, allowing to develop more potential applications of cercosporin.

Cercosporin production by Cercospora coffeicola isolates: spectrophotometry and HPLC quantification and image analysis

“…alchemillicola and Pseudocercosporella capsellae isolates has already been reported by other authors using the SPEC method (Gunasinghe et al 2016;Silva 2018;Vale et al 2019). Cercosporin biosynthesis is affected by external factors such as light, temperature, pH, nutrient supply and incubation time (Jenns et al 1989;Vale et al 2019;Zhou et al 2021). Since the factors mentioned above have been standardized in the present study, possibly the isolates have intrinsic factors that influence the production of the toxin in hyphae, resulting in different cercosporin concentrations.…”

“…The selection of isolates with the ability to produce cercosporin associated with enhancers (e. Bacillus velezensis, Lysinibacillus sp.) will allow more potential industrial applications with cercosporin (Zhou et al 2021).…”

“…The cercosporin produced by Cercospora and some Pseudocercosporella and Colletotrichum species is the best-studied perylenequinone (Jonge et al 2018;Gunasinghe et al 2016). Cercosporin is a highly coveted red-purple polyketide produced by fungal hyphae for its excellent properties of photosensitization, being, therefore, widely investigated for its photophysics, photochemistry and photobiology aspects (Guedes and Eriksson 2007;Daub and Chung 2009;Souza et al 2019;Zhou et al 2021). Furthermore, it has shown potential in medicine regarding the cytotoxic effect on human tumor cells (Mastrangelopoulou et al 2019).…”

Natural product cercosporin as a bioinspired photocatalyst for the synthesis of peptides containing kynurenine via an energy transfer mechanism

“…The increasement of CP amount could further improve the reaction efficiency (Table 1, entry 16). Finally, we also tested other commonly used organic and metal-based photocatalysts such as eosin Y (EY), methylene blue (MB) and fac-Ir, which all gave inferior results (Table 1, entries [17][18][19]. Replacement of O 2 with air did not result in a significantly lower yield, which Scheme 1 Methods for the preparation of peptides containing the kynurenine moiety.…”

“…Thus, instead of the SET mechanism, another promising energy transfer (EnT) mechanism, 15 which is considered as a complementary approach with lower kinetic barriers, 15 d might be an ideal pathway to address these intractable challenges. Bioinspired by the great capacity of the natural product cercosporin (CP) to generate singlet oxygen ( 1 O 2 ) 16 through the EnT pathway, 17 we envisaged that the biomimetic photocatalyst CP, which can be prepared in large quantities through our recently developed biotechnological synthesis method, 18 might provide tremendous potential to address the intractable challenges mentioned above. Herein, to continue our interest in the bioinspired natural product CP-catalyzed photo-mediated catalysis, 17,19 we report an alternative photooxidation for the efficient and selective synthesis of Kyn-containing peptides with the free N –H of the indole catalyzed by the organophotocatalyst CP via an energy transfer mechanism.…”