A Recombinant 12-His Tagged Pyrococcus furiosus Soluble [NiFe]-Hydrogenase I Overexpressed in Thermococcus kodakarensis KOD1 Facilitates Hydrogen-Powered in vitro NADH Regeneration

Metabolic engineering of Caldicellulosiruptor bescii for hydrogen production

Hydrogen is an alternative fuel for transportation vehicles because it is clean, sustainable, and highly flammable. However, the production of hydrogen from lignocellulosic biomass by microorganisms presents challenges. This microbial process involves multiple complex steps, including thermal, chemical, and mechanical treatment of biomass to remove hemicellulose and lignin, as well as enzymatic hydrolysis to solubilize the plant cell walls. These steps not only incur costs but also result in the production of toxic hydrolysates, which inhibit microbial growth. A hyper-thermophilic bacterium of Caldicellulosiruptor bescii can produce hydrogen by decomposing and fermenting plant biomass without the need for conventional pretreatment. It is considered as a consolidated bioprocessing (CBP) microorganism. This review summarizes the basic scientific knowledge and hydrogen-producing capacity of C. bescii. Its genetic system and metabolic engineering strategies to improve hydrogen production are also discussed. KEY POINTS: • Hydrogen is an alternative and eco-friendly fuel. • Caldicellulosiruptor bescii produces hydrogen with a high yield in nature. • Metabolic engineering can make C. bescii to improve hydrogen production.

Biomanufacturing by In Vitro Biotransformation (ivBT) Using Purified Cascade Multi-enzymes

In vitro biotransformation (ivBT) refers to the use of an artificial biological reaction system that employs purified enzymes for the one-pot conversion of low-cost materials into biocommodities such as ethanol, organic acids, and amino acids. Unshackled from cell growth and metabolism, ivBT exhibits distinct advantages compared with metabolic engineering, including but not limited to high engineering flexibility, ease of operation, fast reaction rate, high product yields, and good scalability. These characteristics position ivBT as a promising next-generation biomanufacturing platform. Nevertheless, challenges persist in the enhancement of bulk enzyme preparation methods, the acquisition of enzymes with superior catalytic properties, and the development of sophisticated approaches for pathway design and system optimization. In alignment with the workflow of ivBT development, this chapter presents a systematic introduction to pathway design, enzyme mining and engineering, system construction, and system optimization. The chapter also proffers perspectives on ivBT development.

Biohydrogen production beyond the Thauer limit by precision design of artificial microbial consortia

Dark fermentative biohydrogen (H₂) production could become a key technology for providing renewable energy. Until now, the H₂ yield is restricted to 4 moles of H₂ per mole of glucose, referred to as the "Thauer limit". Here we show, that precision design of artificial microbial consortia increased the H₂ yield to 5.6 mol mol^-1 glucose, 40% higher than the Thauer limit. In addition, the volumetric H₂ production rates of our defined artificial consortia are superior compared to any mono-, co- or multi-culture system reported to date. We hope this study to be a major leap forward in the engineering of artificial microbial consortia through precision design and provide a breakthrough in energy science, biotechnology and ecology. Constructing artificial consortia with this drawing-board approach could in future increase volumetric production rates and yields of other bioprocesses. Our artificial consortia engineering blueprint might pave the way for the development of a H₂ production bioindustry.

High-efficiency transformation of archaea by direct PCR products with its application to directed evolution of a thermostable enzyme

Hyperthermophilic archaea with unique biochemical and physiological characteristics are important organisms for fundamental research of life science and have great potential for biotechnological applications. However, low transformation efficiency of foreign DNA molecules impedes developments in genetic modification tools and industrial applications. In this study, we applied prolonged overlap extension PCR (POE-PCR) to generate multimeric DNA molecules and then transformed them into two hyperthermophilic archaea, Thermococcus kodakarensis KOD1 and Pyrococcus yayanosii A1. This study was the first example to demonstrate the enhanced transformation efficiencies of POE-PCR products by a factor of approximately 100 for T. kodakarensis KOD1 and 8 for P. yayanosii A1, respectively, relative to circular shuttle plasmids. Furthermore, directed evolution of a modestly thermophilic enzyme, Methanothermococcus okinawensis 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), was conducted to obtain more stable ones due to high transformation efficiency of T. kodakarensis (i.e. ~3 × 10⁴  CFU per μg DNA). T. kodakarensis harbouring the most thermostable MoHMGR mutant can grow in the presence of a thermostable antibiotic simvastatin at 85°C and even higher temperatures. This high transformation efficiency technique could not only help develop more hyperthermophilic enzyme mutants via directed evolution but also simplify genetical modification of archaea, which could be novel hosts for industrial biotechnology.