Abstract
Shiraia bambusicola is an important and valuable macrofungus and hypocrellins are its main secondary metabolites which have been widely applied in many medical fields. However, during SSF process of this filamentous fungus, use ratio of corn substrate and dissolved oxygen supply are two main limiting factors, which influence production cost, yield and product quality. To solve these problems, overexpressions of amy365-1 and vgb in S. bambusicola were investigated and three overexpression transformants were constructed. Results demonstrated that expressions and coexpression of AMY365-1 and VHb not only increased the productions of biomass, amylase, hypocrellin, but also up-regulated relative expression levels of four central carbon metabolism genes (pdc, ald, acs, acc) and seven hypocrellin biosynthesis genes (fad, mono, zftf, omef, msf, pks, mco). Furthermore, expression of VHb decreased SSF period. When amy365-1 and vgb were coexpressed, relative expression levels of zftf and pks reached their highest levels at 72 h under liquid fermentation, hypocrellin production reached the highest level 75.85 mg/gds which was 2.99-fold compared with wild type strain within 11 days under SSF, and residual starch of solid substrates was decreased from 35.47 to 14.57%.
Highlights
Shiraia bambusicola is an important and valuable macrofungus in the medical and food industries
SUPER-H168 was chosen as the control strain for analysis of biomass, hypocrellin production, residual sugar and relative expression levels
Hypocrellin production in co-expression strain of AMY365-1 and Vitreoscilla hemoglobin (VHb) reached the highest level 3681 mg/L at 96 h, it was 5.24-fold compared with wild type strain (703 mg/L at 96 h)
Summary
Shiraia bambusicola is an important and valuable macrofungus in the medical and food industries. Hypocrellins are the main secondary metabolites of S. bambusicola, including hypocrellin A, hypocrellin B, hypocrellin C and hypocrellin D (Fang et al 2006), a type of perylenequinone. Abundant ROS cause cellular oxidative stress and kill cells by damaging cellular macromolecules, including lipids, DNA and proteins (Trachootham et al 2008). Based on this characteristic, hypocrellins have been widely applied in many medical fields, such as photodynamic tumor therapy and antivirus treatments (Gao et al 2012; Jin et al 2013). Hypocrellins have been widely applied in many medical fields, such as photodynamic tumor therapy and antivirus treatments (Gao et al 2012; Jin et al 2013) They have been used to treat skin
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