QB3 Postdoc Seminar

Seminar | May 11 | 4:30-5:30 p.m. | 177 Stanley Hall

 QB3 - California Institute for Quantitative Biosciences

Speaker 1: Patrick Rühs (Phillip Messersmith lab)

3D Printing of Bacteria-derived Complex Materials using Functional Living Inks

Abstract
Despite recent advances to control the spatial composition and dynamic functionalities of bacteria embedded in materials, bacterial localization into complex 3D geometries remains a major challenge. Here we demonstrate a 3D printing approach to create bacteria-derived functional materials by combining the natural diverse metabolism of bacteria with the shape design freedom of additive manufacturing (1).
For 3D printing we use a recently developed multimaterial direct ink writing technique (2) which allows us to incorporate bacteria in biocompatible inks within the same 3D printed material. Our bioinks are designed by combining different hydrogels to form a paste-like ink, which after printing is crosslinked by low intensity UV light. To obtain accurate 3D printed structures, we determine the ideal rheological properties prior, during and after printing, demonstrating the effect of the printing steps on the bioink. With this approach we are able to obtain a hydrogel which supports bacteria growth while still maintaining a high shape fidelity in 3D printing.
We embedded bacteria in the biocompatible and functionalized 3D printing ink and printed two types of ‘living materials’ capable of degrading pollutants and of producing medically relevant bacterial cellulose. Furthermore, we demonstrate that bacteria proliferation is a function of viscosity and oxygen availability. By fine-tuning the single ink components, we adjust the viscosity to match the growth profile of our cells. With this printing platform, we envision the use of additive manufacturing materials combined together with cells to be used for new and biomedical applications.

(1) Schaffner, M.*, Rühs, P.A.*, Coulter, F., Kilcher, S., Studart, A.R. 3D printing of bacteria into functional complex materials, Science Advances, Vol. 3, no. 12, eaao6804, (2017)
(2) Kokkinis, D., Schaffner, M. & Studart, A. R. Multimaterial magnetically assisted 3D printing of composite materials. Nature Communications, 6, (2015).

Speaker 2: John Hangasky (Michael Marletta lab)

Co-substrate reactivity of polysaccharide monooxygenases: O2 versus H2O2

Abstract
Enzymatic conversion of polysaccharides into lower molecular weight, soluble oligosaccharides is dependent on the action of hydrolytic and oxidative enzymes. Polysaccharide monooxygenases (PMOs) use an oxidative mechanism to break the glycosidic bond of polymeric carbohydrates, thereby disrupting the crystalline packing and creating new chain ends for hydrolases to act on. PMOs contain a mononuclear Cu(II) center that is directly involved in C–H bond hydroxylation. Molecular oxygen was the accepted co-substrate utilized by this family of enzymes until a recent report indicated reactivity was dependent on H2O2. Although oxygen is acknowledged as the co-substrate utilized for other biological copper-dependent hydroxylations, there is no reason to rule out hydrogen peroxide for PMOs. A detailed analysis of PMO reactivity with H2O2 and O2, in conjunction with high-resolution mass spectrometry measurements, will be presented. These data show that PMOs are capable of using either co-substrate to oxidize the glycosidic linkage of cellulosic substrates, but different molecular mechanisms are accessed that ultimately affect enzyme activity and the products formed.

 yirui.guo@berkeley.edu