Selective fructose production by utilization of glucose liberated during the growth of Cladosporium cladosporioides on inulin or sucrose

Abstract

The growth of Cladosporium cladosporioides in sucrose, inulin and extract of Jerusalem artichoke as sole carbon source have been investigated. The invertase (EC 3.2.1.26) and inulase (EC 3.2.1.7) activities present in the cells produced a glucose-fructose mixture from which glucose was preferentially removed. Results showed that 62–83% of the initial fructose can be recovered from the fermentation in sucrose or an extract of Jerusalem artichoke. The fructose recovered (5g/litre per batch fermentation cycle of 16 h) corresponded to nearly 80% of the total fructose theoretically available. This yield was almost constant in 11 batch cycles using the same cells and fresh sterilized extract of Jerusalem artichoke (0.8% total carbohydrates, w/v) to replace the spent medium and start a new batch cycle. The same high fructose recovery (70%) was achieved with higher total carbohydrate concentration (5%, w/v) in the extract of Jerusalem artichoke, in five batch cycles. However, the time for hydrolysis of all fructans and glucose consumption was much longer (48 h/batch cycle of fermentation at 28°C).