Synthesis of furoic acid from biomasses by sequential catalysis with fish scale-rice husk-based heterogeneous chemocatalyst and dehydrogenase biocatalyst

In this work, furfural was effectively converted to furoic acid (FCA) by using biological macromolecules as raw materials in tandem reaction with chemical biological catalysts. Firstly, a biochar-based heterogeneous catalyst Sn-FS-RH was prepared using equal mass of fish scale (FS) and rice husk (RH) as carriers. Different biomasses (such as poplar wood, winter bamboo shoot shell, corn cob, corn straw, reed leaf, peanut shell, rape straw, and potato shell) were transformed into furfural with Sn-FS-RH in deep eutectic solvent choline chloride:Maleic acid (ChCl:MLA)-H2O (10:90, v/v; 170 degrees C), and the furfural yield from corn cob-derived xylose reached the highest (70.5% yield, based on xylose) after 15 min of catalysis. The mechanism of Sn-FS-RH-catalyzed the trans-formation of lignocellulose to furfural was interpreted in ChCl:MLA-H2O. One liter of xylose-hydrolysate was obtained after acid hydrolysis of biomass. The preparation of FUR was generally carried out in a 10 liter of autoclave reactor containing 75 g biomass, 36 g Sn-FS-RH catalyst, 100 g ChCl:MLA, and 20 g ZnCl2. The reactor was stirred at 170 celcius for 15 min at 500 rpm. It was observed that the by-products (formic acid, levulinic acid, and 5-hydroxymethylfurfural) formed in the transformation of lignocellulose to furfural had somewhat inhibitory effect on the formation of furoic acid from furfural bioconversion. After 24-72 h, Escherichia coli HMFOMUT cells containing dehydrogenase could transform fully furfural derived from different biomass (30-90 mM) into furoic acid. This two-step chemoenzymatic strategy was an efficient way to transform biomacromolecules into bio-furans in a sustainable medium.

Automated summary

In this work, furfural was converted to furoic acid using biological macromolecules and chemical biological catalysts. A heterogeneous catalyst Sn-FS-RH was prepared using fish scale and rice husk as carriers. Different biomasses were transformed into furfural and the highest yield was obtained from corn cob-derived xylose. The by-products formed in the transformation of lignocellulose to furfural had an inhibitory effect on the formation of furoic acid. Escherichia coli HMFOMUT cells could fully transform furfural into furoic acid. This two-step chemoenzymatic strategy was an efficient and sustainable way to convert biomacromolecules into bio-furans.