Optimization of Conditions For Increasing of Saffron Cell Biomass And Crocin Production In Stirred Bioreactor
Abstract Bioreactors provide suitable conditions for the growth of cells and production of secondary metabolites by regulating physical and chemical factors. In this study, first, sucrose, 2-(N-morpholino) ethanesulfonic acid (MES) as a buffering agent and medium pH was optimized in the Erlenmeyer flask. This aim was then pursued in a stirred bioreactor through aeration and pH medium adjustment. Results of the first step showed that Schenk and Hildebrandt (SH) basal medium with naphthalene acetic acid (2 mg.l-1) and 6-benzylaminopurine (1 mg.l-1) supplemented with 2.5 mM of MES and gradually increment of sucrose from 3 to 6% caused to catch the highest cell biomass and crocin production. The spectrophotometry measurement showed that the highest crocin content of the cells was 0.8 mg/g after five weeks. The results of the second part revealed that in the stirred bioreactor, constant pH (5.8) during the growth period is a limited factor for the cell growth and crocin production. Although aeration initially found to be an inhibited factor for the production of crocin, results showed that, if the evaporated volume of water caused by aeration is constituted, it can be an effective factor to increase cell growth rate around 2 folds. In addition, total crocin content of the cells, based on the HPLC could be raised up to 2 mg/g. Based on this study, it can be concluded that MES and gradual increment of sucrose could increasing the cell growth and crocin production. Aeration in bioreactor can increase cell biomass, if the medium volume will be kept constant.