Levulinic acid (LA) is considered to be one of the promising organic bio-platform chemicals and intermediates for the synthesis of fuels, chemicals, and polymers. In the present study, heterogeneous catalytic dehydration of hexose sugars, fructose and glucose, using a strong cation exchange resin (hydrogen form) as an acid catalyst, was performed to produce LA in an aqueous medium. The effect of salts such as NaCl, KCl, CaCl₂, Na₂CO₃, and Na₂SO₄ in the medium on the rate of sugar conversion and LA yield was evaluated. Under optimum reaction conditions, 10% (w/w) fructose was dehydrated to LA (with 74.6% yield) in 10% (w/w) NaCl aqueous solution in 24 h at 110 °C using the catalyst at 30% (w/w sugar). Even 10% (w/w) glucose monohydrate was directly dehydrated to LA (with 70.7% yield) under similar conditions but at 145 °C. This study shows that the salts enhance the rate of catalytic dehydration in the order of Cl^– > CO₃^2– > SO₄^2–. Thus, the combination of high sugar concentration and heterogeneous catalysis in an aqueous system under relatively mild conditions could provide a high-yielding and sustainable process for bio-based LA production.

3-Hydroxypropionic acid (3HP) and acrylic acid (AA) are industrially important platform- and secondary chemical, respectively. Their production from renewable resources by environment-friendly processes is desirable. In the present study, both chemicals were almost quantitatively produced from biodiesel-derived glycerol by an integrated process involving microbial and chemical catalysis. Glycerol was initially converted in a fed-batch mode of operation to equimolar quantities of 3HP and 1,3-propanediol (1,3PDO) under anaerobic conditions using resting cells of Lactobacillus reuteri as a biocatalyst. The feeding rate of glycerol was controlled at 62.5 mg/gCDW.h which is half the maximum metabolic flux of glycerol to 3HP and 1,3PDO through the L. reuteri propanediol-utilization (pdu) pathway to prevent accumulation of the inhibitory intermediate, 3-hydroxypronionaldehyde (3HPA). Subsequently, the cell-free supernatant containing the mixture of 3HP and 1,3PDO was subjected to selective oxidation under aerobic conditions using resting cells of Gluconobacter oxydans where 1,3PDO was quantitatively converted to 3HP in a batch system. The optimum conditions for the bioconversion were 10 g/L substrate and 5.2 g/L cell dry weight. Higher substrate concentrations led to enzyme inhibition and incomplete conversion. The resulting solution of 3HP was dehydrated to AA over titanium dioxide (TiO2) at 230 °C with a yield of >95 %. The present study represents the first report on an integrated process for production of acrylic acid at high purity and -yield from glycerol through 3HP as intermediate without any purification step. The proposed process could have potential for industrial production of 3HP and AA after further optimization.

A facile, rapid process for 5-HMF production at high yield and purity using a green biphasic system.

Lactobacillus reuteri converts glycerol to 3-hydroxypropionic acid (3HP) and 1,3-propanediol (1,3PDO) via 3-hydroxypropionaldehyde (3HPA) as an intermediate using enzymes encoded in its propanediol-utilization (pdu) operon. Since 3HP, 1,3PDO and 3HPA are important building blocks for the bio-based chemical industry, L. reuteri can be an attractive candidate for their production. However, little is known about the kinetics of glycerol utilization in the Pdu pathway in L. reuteri. In this study, the metabolic fluxes through the Pdu pathway were determined as a first step towards optimizing the production of 3HPA, and co-production of 3HP and 1,3PDO from glycerol. Resting cells of wild-type (DSM 20016) and recombinant (RPRB3007, with overexpressed pdu operon) strains were used as biocatalysts.

There is currently an intensive development of sugar-based building blocks toward the production of renewable high-performance plastics. In this context, we report on the synthesis of a rigid diol with a spirocyclic structure via a one-step acid-catalyzed acetalation of fructose-sourced 5-hydroxymethylfurfural and pentaerythritol. Preliminary life cycle assessment (LCA) indicated that the spiro-diol produced 46% less CO₂ emission than bio-based 1,3-propanediol. Polymerizations of the spiro-diol together with another sugar-based flexible 1,6-hexanediol for the production of polyesters and poly(urethane-urea)s were investigated, and reasonably high molecular weights were achieved when up to 20 and 60 mol% spiro-diol was used for polyesters and poly(urethane-urea)s, respectively. The glass transition temperatures (T_gs) of the polyesters and poly(urethane-urea)s significantly increased upon the incorporation of the rigid spirocyclic structure. On the other hand, it was observed that the spiro-diol was heat-sensitive, which could cause coloration and partial crosslinking when >10% (with respect to dicarboxylate) was used for the polyester synthesis at high temperatures. The results indicated that the polymerization conditions have to be carefully controlled under these conditions. However, when the spiro-diol was used for the synthesis of polyurethanes at lower temperature, the side reactions were insignificant. This suggests that the new spiro-diol can be potentially suitable toward the production of sustainable rigid polyurethane materials like coatings or foams, as well as renewable polyesters after further optimization of the polymerization conditions.