NSF/CBET-BSF: Overcoming the Major Challenges to Algal Biohydrogen Production

Arizona State University, Scottsdale AZ

Investigators

Abstract

Hydrogen (H2) is a promising renewable fuel and a valuable commodity industrial gas used in many chemical process industry technologies (e.g. fertilizer synthesis, petroleum refining). The current industrial method to produce hydrogen is steam reformation of natural gas. This produces carbon dioxide while consuming methane, a high-value fuel. In contrast, hydrogen production by photosynthetic microbes makes use of sunlight and abundant resources (e.g. wastewater or seawater) and avoids competition with agriculture for food production. This technology approach has technical barriers to improved performance. As part of the photosynthesis process, molecular oxygen, O2, is formed that poisons the enzymes that produce the hydrogen. The goal of this project is to overcome these limitations. The strategy that will be used is to link the protein machines in the algal cells that make hydrogen to other proteins that could make hydrogen production more efficient. The learnings of this project will also be shared with an outreach program to K-12 students and their teachers for an active learning laboratory project by working with ASU's Global Institute of Sustainability. For industrial competitiveness, algal hydrogen production must be increased by at least 5-fold. Two major challenges limit efficient biological H2 production: inactivation of the hydrogenase enzyme by O2; and limited electron flow from the photosynthetic apparatus to the hydrogenase. To address the first challenge, the hypothesis is that the enzyme can be protected by local microoxic environments created by nearby O2 uptake mechanisms. Several complementary ways to reduce O2 at the vicinity of the hydrogenase will be pursued including use of chimeric proteins in which the hydrogenase is joined with a partner protein capable of reducing O2 or reactive oxygen species (e.g. glucose oxidase, flavodiiron protein). These chimeras will first be tested in vitro and then the most promising ones will be expressed in vivo. Rapid molecular and spectroscopic tests will be used to identify limitations to light-driven hydrogen production in the engineered strains. Several genetic modifications will be utilized to rectify identified limitations in electron flow or H2 production activity. Complementary sets of expertise in the two research groups in the US and Israel will be put to use in the creation, analysis, and optimization of the engineered algal cells. Together the two groups will determine the optimal way to arrange the various new components to make sustained high-level bio-hydrogen production a reality.