PhD thesis topic
Modified tannins to increase the value of bark waste as a source of bioactive feed (ModiFeed)
(1) To find rare tannins and produce tannin modifications by multiple different methods.
(2) To unravel how tannin structures may be altered by incorrect sample preparation techniques.
(3) To understand how tannin modification affects their chemical properties and in vitro bioactivities.
(4) To find out the structure-activity relationships for modified tannins and their anthelmintic activities.
There are many tannin sources available e.g. from the side streams of wood industry, but those tannins do not have optimal structures for the activity and stability. The Natural Chemistry Research Group (NCRG) has good knowledge of active tannin types and their chemical properties. Recently, the group has created several UPLC-MS/MS based methods for the qualitative and quantitative analysis of plant polyhenols. They have found also clear structure-activity relationships between ruminant-related bioactivities and one specific class of tannins, i.e. hydrolysable tannins.
My work is part of the ModiFeed project and this research entity is part of the BioFuture strategy of the University of Turku. ModiFeed and my PhD work will build on this knowledge of NCRG and produce several new types of active tannin products from the industry side streams. This will be accompanied by the state-of-the-art chemical analysis, anthelmintic and antimethanogenic assays that are done in Finland, Denmark, France and the Netherlands. The ultimate goal is to reveal the best ways to produce active and stable tannin products for the more efficient commercial utilization of waste materials as sources of bioactive additives in the feeds of the future.
I will utilize biotechnology, chemistry and parasitology to achieve the objectives. I aim to produce tools for the production of valuable products such as modified bioactive tannins that can be used as feed additives to battle world-wide infections of ruminants with intestinal nematodes. I will develop technologies and processes that support biotechnology-based production of bioactive modified tannins. My work will also improve the production potential of animals via the bioactive feed components. The target is to reduce the raw material utilization and decrease the waste generation by creating these modified bioactive tannin products from the thousands of tons of bark waste annually produced e.g. by Finnish wood industry.
Results so far
To develop the production methods of such rare tannins we used a unique method where tannins are modified by oxidation in alkaline conditions. It included the collection of 300 plant samples from the Botanical Garden of the University of Turku, Finland. In addition, 7 commercial tannin preparations were investigated. From the preliminary screening 130 plant samples has procyanidin and prodelphinidin rich oligomers and polymers, which has polyphenol oxidase enzyme activity. The tannins in these plant samples were extracted and analyzed as such by UPLC connected to Waters XEVO TQ triple quadrupole mass spectrometer. Then the plant extracts were oxidized by an oxidation test using pH 10 buffer. Altogether, 37 samples contained proanthocyanidins that were uniquely oxidized or otherwise modified in alkaline conditions. These samples were further studied by ThermoScientific QExactive Orbitrap that is one of the flagships of high-resolution mass spectrometers, in order to characterize the modified tannin structures. In addition, the proanthocyanidin oligomers and polymers in oxidized and non-oxidized samples were quantified by Multiple Reaction Monitoring (MRM) methods by UPLC-MS/MS. These results are very interesting and show that rare tannins have novel modification products. It suggested that prodelphinidin (PD) rich oligomers has higher chances to modify the tannin structure in the alkaline condition whereas procyanidin (PC) rich oligomers and polymers has less chances to modify the structure. However, the PC helps to stable the tannin structure. On the other hand, if the PD is absent in the sample then the structure is more stable or no oxidation occur.