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

氢（H2）是一种很有前途的可再生燃料，也是一种有价值的商品工业气体，用于许多化学过程工业技术（如化肥合成、石油炼制）。目前的工业制氢方法是天然气的蒸汽重整。这在消耗高价值燃料甲烷的同时产生二氧化碳。相比之下，光合微生物制氢利用阳光和丰富的资源（如废水或海水），避免了与农业在粮食生产方面的竞争。这种技术方法在提高性能方面存在技术障碍。作为光合作用过程的一部分，分子氧（O2）的形成毒害了产生氢的酶。这个项目的目标就是克服这些限制。将使用的策略是将藻类细胞中制造氢的蛋白质机器与其他可以提高氢生产效率的蛋白质连接起来。通过与亚利桑那州立大学全球可持续发展研究所合作，该项目的学习成果也将与K-12学生及其教师的积极学习实验室项目分享。为了提高产业竞争力，藻氢产量必须至少增加5倍。两个主要的挑战限制了高效的生物制氢：氢酶被O2失活；从光合作用装置到氢化酶的电子流动有限。为了解决第一个挑战，假设是酶可以被附近氧气摄取机制产生的局部微氧环境保护。在氢化酶附近还原O2的几种互补方法将被寻求，包括使用嵌合蛋白，其中氢化酶与能够还原O2或活性氧的伙伴蛋白（例如葡萄糖氧化酶，黄二铁蛋白）连接。这些嵌合体将首先在体外进行测试，然后最有希望的嵌合体将在体内表达。快速分子和光谱测试将用于确定工程菌株中光驱动制氢的限制。一些基因修饰将被用来纠正在电子流或H2生产活动中确定的限制。美国和以色列两个研究小组的互补专业知识将用于工程藻类细胞的创建、分析和优化。这两个小组将共同确定安排各种新组件的最佳方式，以实现持续的高水平生物氢生产。

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.