Improvement of hypocrellin production by a new fungal source and optimization of cultivation conditions

Abstract

Hypocrellins is regarded as the new generation of potential photosensitizer in the photodynamic therapy. However, the current production of HA in large quantity is limited, whether extracted from the fruit bodies of Hypcrella bambusae and Shiraia bambusicola, or its fermented mycelia. To break through the bottleneck, we screened over 350 fungal strains from the uncommon moso bamboo (Phyllostachys edulis) seeds, and acquired 14 isolates of Shiraia sp. Hypocrellins were generally extracted from the stroma of S. bambusicola, and however the hypocrellin-producing strains in our study were identified as endophytic fungi, where several of them exhibited significantly high content of hypocrellins. One of them, a newly isolated Shiraia sp. strain ZZZ816 was selected for further research. The hypocrellin production conditions of the strain ZZZ816 under submerged fermentation were optimized by one-factor-at-a-time and orthogonal experiment design. The optimum parameters for the quid fermentation were determined as follows: incubation time (144 h), initial pH (6.0), volume of medium (100/250 mL), rotary speed (130 rpm), mycelial age (60 h) and inoculation level (10%). The optimum culture medium constituents were determined as follows: yeast extract 20g/L, malt sugar 40g/L, FeSO 4 ¢H 2 O 0.5g/L, urea 4.0g/L, MgS0 4 ¢7H 2 0 0.5g/L and initial pH 5.0. Using submerged fermentation of the optimum production conditions, the maximum content of hypocrellin A from the strain ZZZ816 was 921.6 mg/L, more than the other industrial strains published in the previous reports. The results demonstrated that Shiraia sp. strain ZZZ816 could enhance the hypocrellin production tremendously with optimizing the fermentation progress.

Optimisation of hypocrellin production in Shiraia -like fungi via genetic modification involving a transcription factor gene and a putative monooxygenase gene

“…The wild type and transformed strains were cultured in PDB, and then the mycelia were dried and soaked in methanol. The cell-associated hypocrellins were extracted as described previously for S. bambusicola (Shen et al 2016 ). The content of the extracts was analysed using an Agilent 1200 Series HPLC system equipped with a Kromasil 100-5 C18 column (250 mm × 4.6 mm).…”

Efficient agrobacterium-mediated transformation ofShiraia bambusicolaand activation of a specific transcription factor for hypocrellin production

“…Extraction of cell-associated hypocrellins from S. bambusicola was done as described by Shen et al [17]. The content of the extracts was analyzed by an Agilent 1200 Series HPLC system equipped with a Kromasil 100-5 C18 (250 Â 4.6 mm).…”

“…Even among the present studies with diverse modified strains, such as S. bambusicola zzz816 and Shiraia sp. Slf14, the strain CNU103846 was still at the top of the list [17,26]. It was noticeable that the premature overexpression of SbTF1 hindered the normal growth of mycelia; therefore, the final mass was significantly lower than in the primary strain.…”

“…In the general, the PDA medium is adapted to the S. bambusicola stains, but some important strains only produce hypocrellins in addition to Triton X-100 [27,28]. The employment of other media would receive more restrictions and would often eliminate the red pigments, especially including the natural components [17,29,30]. The wave length and intensity of light could also determine the biosynthetic efficiency, so the increase of the production has to be limited to the update of equipment [31][32][33].…”