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Doctoral thesis: The importance of oxygen availability in industrially important plant-based bioprocesses

08.10.2007

Wilhelmson used gene technology to study the role of oxygen in the growth and hyoscyamine production of Egyptian henbane hairy root cultivations and in the malting of barley.

Hyoscyamine is a pharmaceutical compound that is mainly isolated from plants because other production methods are not economically feasible. Instead of isolation from plants, hyoscyamine could be produced in hairy root cultivations of Egyptian henbane; however, in industrial scale processes oxygen transfer to the roots becomes difficult.

Barley is the main raw material in beer production. The lack of oxygen has traditionally been believed to restrict the germination of barley in the malting process and therefore aeration is used during the process. However, oxygen added through aeration does not necessarily reach the barley embryo because it may be consumed by microbes and in chemical reactions.

Wilhelmson transferred the vhb gene encoding an efficient haemoglobin from the Vitreoscilla microbe to Egyptian henbane and barley. The hypothesis was that the haemoglobin would improve growth and hyoscyamine production of the Egyptian henbane root cultures and the germination rate of barley. In addition, she studied the effect of aeration on the processes.

The study showed that the haemoglobin of Vitreoscilla improved the growth of root cultures but did not have a significant effect on hyoscyamine production. The effect of Vitreoscilla haemoglobin was not identical to that of aeration indicating that mechanisms other than those directly related to oxygen concentration are involved. The results will help in further development of pharmaceutical production from hairy roots.

The importance of oxygen deficiency in malting was highly dependent on the stage of the process. Wilhelmson proved that oxygen deficiency is a natural and inevitable stage in barley germination, and aeration did not reduce the oxygen deficiency of barely during the early stages of germination. Moreover, Vitreoscilla haemoglobin did not improve germination; on the contrary, it even slowed down germination slightly. A certain degree of oxygen deficiency may actually be favourable for germination because it generates nitric oxide, which accelerates germination. The research showed that the need for aeration increases as the malting process proceeds. Malt houses can utilise the results in timing the aeration of the malting process.

VTT, Research Scientist, Annika Wilhelmson, M.Sc., will defend her doctoral thesis on 12 October 2007 at noon at the Helsinki University of Technology (Street address: Kemistintie 1, Auditorium Ke2, Espoo, Finland).


Doctoral thesis: The importance of oxygen availability in two plant-based bioprocesses: hairy root cultivation and malting.