Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Chlorella is a promising alternative source of lutein, as it can be cultivated heterotrophically with high efficiency. In this study, the carotenoids in Chlorella pyrenoidosa heterotrophically cultivated in a 19-litre fermentor have been analyzed and determined by using HPLC and HPLC-MS. A biochemical system theory (BST) model was developed for understanding the regulatory features of carotenoid metabolism during the batch cultivation. Factors that influence lutein production by C. pyrenoidosa were discussed based on the model. It shows that low flux for lycopene formation is the major bottleneck for lutein production, while by-product syntheses and inhibitions affect the cellular lutein content much less. However, with further increase of the cellular lutein content, the inhibition on lycopene formation by lutein may become a limiting factor. Although speculative, these results may provide useful information for further elucidation of the regulatory mechanisms of carotenoid biosynthesis in Chlorella and modifying its metabolic network to enhance lutein production.Alga Chlorella mogući je izvor luteina, jer se može uspješno uzgajati u heterotrofnim uvjetima. Stoga su u radu primjenom HPLC i HPLC-MS metoda ispitani karotenoidi iz alge Chlorella pyrenoidosa, uzgojene u heterotrofnim uvjetima u bioreaktoru volumena 19 L. Razvijen je model biokemijskog teorijskog sustava za razumijevanje regulacije metabolizma karotenoida pri šaržnom uzgoju. Na temelju tog modela razmatrani su faktori koji utječu na proizvodnju luteina s pomoću C. pyrenoidosa. Utvrđeno je da „usko grlo” u proizvodnji luteina nastaje zbog slabog metaboličkog toka sinteze likopena, a da nastajanje nusprodukata i njihov inhibicijski učinak puno manje utječu na količinu luteina u stanicama. Međutim, povećanje količine luteina u stanicama može inhibirati sintezu likopena i stoga postati ograničavajući faktor u proizvodnji. Ovi rezultati, iako još nepotvrđeni, mogu dati korisne informacije za pojašnjenje mehanizma regulacije biosinteze karotenoida u algi Chlorella i modifikaciju metaboličkog procesa radi dobivanja veće količine luteina
