Bioproducts from renewable methanol: The paraformaldehyde approach

Abstract

Green methanol as feedstock in biotech operations at large scales is receiving in-depth attention for the production of Single Cell Protein (SCP) and circular chemicals. Several decades ago, cheap fossil-derived methanol was seen as an attractive feedstock. Now, renewable rather than fossil-derived methanol is in focus since its utilization does not depend on fossil resources and importantly it does not compete with food sources. Despite decade-long efforts, the biotech approaches have not been successful in generating economically viable large-scale production based on methanol. This impressive negative track record is to be attributed to the relatively reduced chemical nature of methanol, which implies excessive oxygen demands during fermentations. Hence, for large-scale methanol fermentations, it is essential to minimize oxygen budgets to arrive at economically-viable production processes. In this short communication, a new approach is described in reducing the oxygen footprint by employing the less-reduced compound paraformaldehyde which, via standard procedures, can be obtained chemically from methanol. It is a water-insoluble polymer, which slowly releases formaldehyde at ambient temperatures depending on either pH or temperature. Three methylotrophic microbes were demonstrated to metabolize formaldehyde as chemically released from the non-toxic paraformaldehyde. Methylophilus methylotrophus kept the monomeric formaldehyde below the detection limit in a stirred-tank bioreactor during a 20-hour run on paraformaldehyde. Based on the current work, it is concluded that paraformaldehyde is a highly-suitable feedstock for producing either SCP or numerous circular chemicals as derived from renewable methanol.