Nicholas George Watanabe

Bio: Nicholas George Watanabe is an academic researcher from University of California, Berkeley. The author has co-authored 1 publications.

Green Chemistry, Biocatalysis and the Chemical Industry of the Future.

Abstract: In the movement to decarbonize our economy and move away from fossil fuels we will need to harness the waste products of our activities, such as waste lignocellulose, methane and carbon dioxide. Our wastes need to be integrated into a circular economy where used products are recycled into a manufacturing carbon cycle. Key to this will be the recycling of plastics at the resin and monomer levels. Biotechnology is well suited to a future chemical industry that must adapt to widely distributed and diverse biological chemical feedstocks. Our increasing mastery of biotechnology is allowing us to develop enzymes and organisms that can synthesize a widening selection of desirable bulk chemicals, including plastics, at commercially viable productivities. Integration of bioreactors with electrochemical systems will permit new production opportunities with enhanced productivities and the advantage of using a low-carbon electricity from renewable and sustainable sources.

Dissolved Organic Matter Acting as a Microbial Photosensitizer Drives Photoelectrotrophic Denitrification.

Abstract: The biogeochemical fates of dissolved organic matter (DOM) show important environmental significance in aqueous ecosystems. However, the current understanding of the trophic relationship between DOM and microorganisms limits the ability of DOM to serve as a heterotrophic substrate or electron shuttle for microorganisms. In this work, we provide the first evidence of photoelectrophy, a new trophic linkage, that occurs between DOM and nonphototrophic microorganisms. Specifically, the photoelectrotrophic denitrification process was demonstrated in a Thiobacillus denitrificans-DOM coupled system, in which DOM acted as a microbial photosensitizer to drive the model denitrifier nitrate reduction. The reduction of nitrate followed a pseudo-first-order reaction with a kinetic constant of 0.06 ± 0.003 h-1, and the dominant nitrogenous product was nitrogen. The significant upregulated (p < 0.01) expression of denitrifying genes, including nar, nir, nor, and nos, supported that the conversion of nitrate to nitrogen was the microorganism-mediated process. Interestingly, the photoelectrophic process triggered by DOM photosensitization promotes humification of DOM itself, an almost opposite trend of pure DOM irradiation. The finding not only reveals a so far overlooked role of DOM serving as the microbial photosensitizer in sunlit aqueous ecosystems but also suggests a strategy for promoting sunlight-driven denitrification in surface environments.

Emerging Trends in Nanomaterials for Photosynthetic Biohybrid Systems

Abstract: Global warming and climate change are among the most immediate challenges confronting humans in the 21st century. Artificial photosynthesis represents a promising approach to mitigating the environmental crisis. Recently, people demonstrated that interfacing semiconductor, polymer, or metal-based nanomaterials with specific bacteria can generate built-in artificial photosynthetic systems, enabling solar-to-fuel conversion by forming a basic photosynthetic unit from a network of light-harvesting receptors, molecular water splitting and CO2, or proton reduction machinery. As a cutting-edge research direction, several strategies have been employed to create the artificial photosynthetic biohybrids. Notably, understanding of the molecular basis of these photosynthetic biohybrid systems is the key to improving the solar-to-chemical conversion efficiency. In the current review, we highlight the study of charge uptake channels in biohybrid artificial photosynthetic systems using various nanomaterials and microbes. We emphasize the importance of fully understanding the structures and operating mechanisms of these hybrid systems, as well as the criterion to select suitable microbes and photosensitized nanomaterials.

Self-Assembled Nanoscale Manganese Oxides Enhance Carbon Capture by Diatoms.

Abstract: Continuous CO2 emissions from human activities increase atmospheric CO2 concentrations and affect global climate change. The carbon storage capacity of the ocean is 20-fold higher than that of the land, and diatoms contribute to approximately 40% of carbon capture in the ocean. Manganese (Mn) is a major driver of marine phytoplankton growth and the marine carbon pump. Here, we discovered self-assembled manganese oxides (MnOx) for CO2 fixation in a diatom-based biohybrid system. MnOx shared key features (e.g., di-μ-oxo-bridged Mn-Mn) with the Mn4CaO5 cluster of the biological catalyst in photosystem II and promoted photosynthesis and carbon capture by diatoms/MnOx. The CO2 capture capacity of diatoms/MnOx was 1.5-fold higher than that of diatoms alone. Diatoms/MnOx easily allocated carbon into proteins and lipids instead of carbohydrates. Metabolomics showed that the contents of several metabolites (e.g., lysine and inositol) were positively associated with increased CO2 capture. Diatoms/MnOx upregulated six genes encoding photosynthesis core proteins and a key rate-limiting enzyme (Rubisco, ribulose 1,5-bisphosphate carboxylase-oxygenase) in the Calvin-Benson-Bassham carbon assimilation cycle, revealing the link between MnOx and photosynthesis. These findings provide a route for offsetting anthropogenic CO2 emissions and inspiration for self-assembled biohybrid systems for carbon capture by marine phytoplankton.