Leveraging agricultural waste manipulation using a novel resveratrol-producing endophytic fungus, Cladosporium sphaerospermum AH26: optimization and enzymatic investigation

Abstract

Resveratrol (RES) is utilized in multiple pharmaceutical and industrial applications. Rising global demand has required immediate novel production solutions for sustainable RES supply. Endophytic fungi are a promising source for RES production; however, their conventional culture impedes economic viability. This study aimed to leverage agricultural wastes as a low-cost carbon source for improving RES productivity alongside the associated hydrolytic enzymatic activities using grapevine-derived endophytic fungus Cladosporium sphaerospermum AH26. C. sphaerospermum was isolated from the stem tissues of grapevine (Vitis vinifera L. Starlight cultivar) and identified by internal transcribed spacer sequencing. The RES-producing capability of AH26 was assessed on potato dextrose broth medium (PDB) and on different agricultural wastes, such as banana peel, wheat straw, and sugarcane bagasse. Thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) were employed for the qualitative and quantitative analysis of RES production, respectively. Hydrolytic enzyme activities were initially screened on agar plates and subsequently quantified using a dinitrosalicylic acid-based assay. Optimization of cultivation conditions for maximizing RES productivity on agricultural wastes was achieved through response surface methodology (RSM) using Box–Behnken design. C. sphaerospermum showed significant efficacy for RES production when cultivated on PDB, banana peel, wheat straw, and sugarcane bagasse, yielding total concentrations of 42.30 µg/mL, 41.78 µg/mL, 39.59 µg/mL, and 40.33 μg/mL, respectively. RSM optimization of agricultural waste cultivation conditions resulted in 2.7-, 3.4-, and 4.7-fold increases in RES concentration on banana peel, wheat straw, and sugarcane bagasse, respectively. Analysis of variance revealed that the interaction between temperature and other cultivation parameters, including incubation period, pH, and substrate concentration, significantly affected RES production. The analysis of hydrolytic enzymes demonstrated a positive correlation between enzymatic activity and RES productivity by C. sphaerospermum. Our findings identified C. sphaerospermum AH26 strain as a promising novel and efficient strain for RES production and demonstrated the potential of agricultural waste-based cultivation as a viable economic and sustainable strategy for the cost-effective production of RES by mycoendophytes.