[P003] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P02-263] Investigation on fed-batch cultivation of Euglena gracilis on beet molasses

○Ayaka Yamamoto¹, Masahiro Hayashi¹ (1. University of Miyazaki (Japan))

Keywords:

Euglena gracilis,beet molasses,fed-batch cultivation,DO-stat control

Euglena gracilis is a member of flagellate eucaryotes, and it accumulates a β-1,3-glucan called paramylon as a storage substance in the cells. Recently paramylon has been developed as raw materials for bioplastics and nanofibers. Another its storage substance, wax esters transformed from paramylon under anaerobic condition, is also tried to utilize for biofuels. Thus, Euglena is expected as sustainable chemical raw materials. For the industrial utilization of Euglena, the high yields of both biomass and paramylon are highly needed. As for the yields or efficiency of mass production, the heterotrophic cultivation has much advantage compare to autotrophic cultivation. In the case of heterotrophic cultivation, however, large amount (around 50%) of carbon source, such as sugars, are consumed by the respiration of Euglena. Therefore, it is required to use cheaper and sustainable carbon sources for the industrial cultivation. In this study, a beet molasses, byproduct of sugar production, was used as a carbon source of Euglena cultivation. For the sustainable and industrial production of Euglena, efficient fed-batch cultivation of Euglena using beet molasses that is inedible and unused resources as a carbon source was investigated. Fed-batch culture was carried out in 2L-jarfermentors under DO-stat control. As Euglena did not assimilate sucrose in the molasses, invertase was added into the medium with an inoculate. Twice a day, cellular yields were determined by drying the culture for 5h at 105 ℃ after washing the cells. The residual glucose, fructose, and sucrose concentrations were measured by HPLC. Paramylon contents were analyzed by the phenol sulfuric acid method. As a growth of Euglena in the medium containing beet molasses as a sole carbon source was suppressed, the Euglena strain was adapted beet molasses as a carbon source for several months. The fed-batch culture of adapted Euglena strain gave the cellular yield 51.77g/L for 11days cultivation. This result was twice that of non-adapted strain. In addition, it confirmed that DO-stat control was working normally during fed-batch cultivation of adapted Euglena.In this study, it was shown that molasses can be used as a carbon source for Euglena cultivation. Moreover, it is expected that effects of components in molasses to Euglena yield will become clear by a metabolic analysis of molasses adapted strain from now on.