title: Production of citrinin-free Monascus pigments by submerged culture at low pH.
abstract: Microbial fermentation of citrinin-free Monascus pigments is of great interest to meet the demand of food safety. In the present work, the effect of various nitrogen sources, such as monosodium glutamate (MSG), cornmeal, (NH4)₂SO₄, and NaNO₃, on Monascus fermentation was examined under different initial pH conditions. The composition of Monascus pigments and the final pH of fermentation broth after Monascus fermentation were determined. It was found that nitrogen source was directly related to the final pH and the final pH regulated the composition of Monascus pigments and the biosynthesis of citrinin. Thus, an ideal nitrogen source can be selected to control the final pH and then the citrinin biosynthesis. Citrinin-free orange pigments were produced at extremely low initial pH in the medium with (NH4)₂SO₄ or MSG as nitrogen source. No citrinin biosynthesis at extremely low pH was further confirmed by extractive fermentation of intracellular pigments in the nonionic surfactant Triton X-100 micelle aqueous solution. This is the first report about the production of citrinin-free Monascus pigments at extremely low pH.
authors.affiliation: School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, PR China; School of Biological Science and Engineering, South China University of Technology, Guangzhou 510006, PR China.
authors.forename: Biyu
authors.initials: B
authors.lastname: Kang
authors.affiliation: State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai 200240, PR China.
authors.forename: Xuehong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: School of Biological Science and Engineering, South China University of Technology, Guangzhou 510006, PR China.
authors.forename: Zhenqiang
authors.initials: Z
authors.lastname: Wu
authors.affiliation: School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, PR China; State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai 200240, PR China. Electronic address: zlwang@sjtu.edu.cn.
authors.forename: Zhilong
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Chemical Engineering, Pusan National University, Pusan 609-735, South Korea.
authors.forename: Sunghoon
authors.initials: S
authors.lastname: Park
mesh_terms: D000645:Ammonium Sulfate / Q000378:metabolism; D002855:Chromatography, Thin Layer; D002953:Citrinin / Q000032:analysis; D003470:Culture Media / Q000494:pharmacology; D005285:Fermentation; D005433:Flour; D005506:Food Contamination / Q000517:prevention & control; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D032741:Monascus / Q000254:growth & development / Q000378:metabolism*; D009172:Mycology / Q000379:methods*; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D017830:Octoxynol; D010860:Pigments, Biological / Q000096:biosynthesis* / Q000302:isolation & purification; D012970:Sodium Glutamate / Q000378:metabolism; D012996:Solutions; D003313:Zea mays
chemical_list: D003470:Culture Media; D008823:Micelles; D009566:Nitrates; D010860:Pigments, Biological; D012996:Solutions; D002953:Citrinin; C031618:sodium nitrate; D017830:Octoxynol; D009584:Nitrogen; D000645:Ammonium Sulfate; D012970:Sodium Glutamate
keywords: Citrinin; Monascus pigments; Nitrogen source; Secondary metabolite; pH