Unique features of several microbial α-amylases active on soluble and native starch

June 3 Fean D. Sarian will defend his PhD research on the action of amylases on native granular starch. The PhD of F. D. Sarian is the first of the new research group Aquatic Biotechnology and Bioproduct Engineering (ENTEG).

PhD ceremony:   F.D. Sarian, MSc
When:               June 03, 2016
Start:                 09:00
Promotors:       prof. dr. M.J.E.C. (Marc) van der Maarel, prof. dr. L. (Lubbert) Dijkhuizen
Where:            Academy building RUG
Faculty:            Mathematics and Natural Sciences
Dissertation:     http://hdl.handle.net/11370/e99745ad-4225-4293-9911-0a7d6c8079ef

Abstract
Starch is the main energy store of major agricultural crops such as corn, potato, rice and wheat. Various amylase type enzymes are used to convert cooked starch to glucose that goes into bioethanol fermentation. Only a few amylase type enzymes have been described that can act on the starch granule itself. Granular starch has a complex crystalline structure that prevents most amylases to directly act on it. In this PhD thesis the action of several amylases on native granular starch was studied in detail. From the wastewater treatment plant of a potato starch factory of AVEBE, a microbial strain specialized in the degradation of potato starch granules was isolated. This isolate possesses a multi domain amylase with several starch binding and fibronectin modules, enabling a rapid degradation of potato starch granules. Deletion of multiple domains resulted in a loss of the granule degrading capacity of this amylase. The modular organization was not found in an amylase obtained from a microbial strain living in a sea anemone from Jellyfish lake, Kakaban Island, Indonesia. This amylase showed very little activity towards granular starch, which is not surprising as this lake has no starch. The substrate for this amylase enzyme is very likely glycogen present in the sea anemone. These results demonstrate that starch granules are inert and require specialized amylase enzymes to be completely degraded. Such special amylase enzymes could be used in a non-cooking starch conversion process, reducing the amount of energy required in the production of glucose syrups for bioethanol fermentation.