title: Effects of different glycerol feeding strategies on S-adenosyl-l-methionine biosynthesis by P(GAP)-driven Pichia pastoris overexpressing methionine adenosyltransferase.
abstract: Methionine adenosyltransferase (MAT) was overexpressed within Pichia pastoris employing the promoter of glyceraldehyde-3-phosphate dehydrogenase gene (P(GAP)), to biosynthesize S-adenosyl-l-methionine (SAM). Effects of five glycerol feeding tactics on MAT activity were first investigated. Strategies A-C were based on limited feeding correlated with dissolved oxygen (DO) at 50.0%, 25.0% and 0.0%, respectively. For strategies D and E, unlimited supplementation was executed by pulsed feeding mode. Gradual decline (2-0%) (w:v) of the residual glycerol level was shown between any two pulses in strategy D, while a nearly stable content (2%) throughout fed-batch cultivation with strategy E. With shifting strategies A-E in alphabetical order, gradual improvements of MAT activities were achieved, with the maximum of 9.05Ug(-1) dried biomass for strategy E, since the specific glycerol consumption rate (F(G)) ascended due to the elevated specific oxygen uptake rate (qO(2)). The success was ascribed to the enhancement of oxygen transfer rate (OTR), because 2% glycerol improved oxygen saturation content in broth (C*) and volumetric oxygen transfer coefficient (k(L)a). Strategy E also led to the highest values of ATP and biomass besides MAT. Consequently, the highest SAM yield and volumetric level were obtained at 0.058gg(-1) and 9.26gl(-1), respectively.
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, P R China.
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Hu
authors.forename: Ju
authors.initials: J
authors.lastname: Chu
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Zhang
authors.forename: Si-Liang
authors.initials: SL
authors.lastname: Zhang
authors.forename: Ying-Ping
authors.initials: YP
authors.lastname: Zhuang
authors.forename: Yong-Hong
authors.initials: YH
authors.lastname: Wang
authors.forename: Mei-Jin
authors.initials: MJ
authors.lastname: Guo
authors.forename: Hua-Xin
authors.initials: HX
authors.lastname: Chen
authors.forename: Zhong-Yi
authors.initials: ZY
authors.lastname: Yuan
mesh_terms: D019149:Bioreactors; D003470:Culture Media; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism*; D008716:Methionine Adenosyltransferase / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010843:Pichia / Q000254:growth & development / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000096:biosynthesis*
chemical_list: D003470:Culture Media; D012436:S-Adenosylmethionine; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D008716:Methionine Adenosyltransferase; D005990:Glycerol; D010100:Oxygen