The research activities have been mostly focused on the development of the three main objectives of the NIBIOX project:
Objective 1. Technological development and fabrication of self-sufficient and facultative anaerobic heterogeneous biocatalysts. This family of biocatalysts is considered what we call the minimum value product (MVP) NIBIOX will deliver. Different Nitrate reductases were selected, and their activities for nitrate oxidation in the presence of either NADPH or NADH were tested. As a result, we selected the most versatile one to oxidize nitrate with both NADH and NADPH. This enzyme was then co-immobilized with an alcohol dehydrogenase and NADH cofactor on different carriers, and its functional properties (activity and stability) were characterized. The carrier that retained the highest activity and stability of both enzymes upon immobilization was selected for process intensification in objective 2.
Objective 2. Validation of optimal self-sufficient heterogeneous biocatalyst (MVP) as an enabling technology to oxidize alcohols in the absence of oxygen. The MVP was tested for the oxidation of benzyl alcohol as a model oxidation, both in batch and in flow under oxygen-limited conditions. Using nitrate as oxidant and the MVP herein developed, we achieved similar volumetric productivity and product yield as using the conventional biooxidation approach using NADH oxidase and molecular oxygen as ultimate electron donor, but higher
Objective 3. Market potential and sustainability assessment of MVP through estimation of fabrication costs and sustainable metrics of a model alcohol oxidation performed with the MVP. Our assessment has provided guidelines to improve the sustainability of PoC technology based on the MVP developed. Higher substrate loadings and conversions at lower reaction times must be achieved to enable proper resource use, with better economic and environmental outcomes. Moreover, solvent optimization at the extractive downstream should focus on the solvent-to-reactor-volume ratio, on enabling solvent recycling, and on promoting biogenic solvents, to ensure higher carbon neutrality in the inevitable incineration of the (largely recycled) spent organic solvents. Regarding the IP and market analysis, we concluded that the NIBIOX concept is highly innovative and holds significant promise for various applications. Given its current proof-of-concept stage, besides IP protection, further development through follow-up projects is recommended – both from academic funding to industrial-driven cooperations –, to explore the full potential and practical implementation.
