Three ammonium‐cationic zeolites (ferrierite, ZSM5, and zeolite BETA) are individually analyzed to produce branched‐chain fatty acid (i.e., isostearic acid) from unsaturated linear‐chain fatty acid (ulc‐FA) with up to 98% conversion and 80% selectivity. The SiO2/Al2O3 molar ratio of zeolite, amount of water and choice of additive are found to be the key factors for the efficiency of zeolites in this particular reaction. Detailed characterization of zeolites supports the optimization parameters to produce the best results. Large scale production of isostearic acid achieving a 76% selectivity and 96% conversion demonstrates the potential of this system's capability at the pilot scale. Variation in isomeric composition of branched‐chain fatty acid (bc‐FA) product is observed for the three different catalytic methods. Dimer production due to interaction with the external acidic surface of these zeolites has been observed, but it can be suppressed. Practical Application: Lubricant, cosmetic and surfactant fields are examples where these biodegradable isostearic acid and other bc‐FA materials are applied. Three ammonium cationic zeolites (i.e., ferrierite, BETA, ZSM‐5) are used to produce the iso‐oleic acid (precursor of isostearic acid) with high selectivity. The iso‐oleic acid products are found to have different isomeric compositions which could potentially expand the application of the isostearic acid.

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Three new iso‐oleic ester derivatives (i.e., isopropyl ester (IOA‐iPrE, 6), n‐butyl ester (IOA‐n‐BuE, 7), and 2‐ethylhexyl ester (IOA‐2‐EHE, 8)) were synthesized from iso‐oleic acid (IOA, 4) using a standard esterification method. These esterified alcohols were chosen because of their bulky and branched‐chain alkyl groups which can reduce melting point in comparison to a smaller alkyl group such as methyl ester. The differential scanning calorimetry (DSC), cloud point and pour point results showed that esters 6, 7, and 8 had much lower melting transition temperatures and cold flow properties than the methyl (IOA–FAME, 5) and parent 4. The oxidative and thermal stability by pressure (P‐DSC) and thermogravimetric analysis (TGA) results also showed a very similar trend where the bulkier and branched‐chain alkyl esters had better stability than the smaller headgroup esters. Practical applications: Since saturated fats have high melting points, they are solids which can be harmful to our health and can cause damage to machinery. There is an urgent need to develop methods to produce fats with low melting points to replace the unwanted fats. In this paper, a series of modified branched‐chain fatty acid ester derivatives (i.e., iso‐oleic acid esters) that are liquid at room temperature with enhanced fluidity were synthesized. These ester fats have been found to perform much better than the original fatty acids and saturated fats. These findings are important as these iso‐oleic ester fats can potentially replace solid materials which are often problematic at low temperatures. Iso‐oleic ester derivatives containing bulky and branched‐chain alkyl groups exhibit reduce melting point in comparison to a smaller alkyl group such as methyl ester.

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Developing integrated biorefineries requires the generation of high-value co-products produced alongside cellulosic ethanol. Most industrial yeast strains produce ethanol at high titers, but the small profit margins for generating ethanol require that additional high-value chemicals be generated to improve revenue. The aim of this research was to boost xylose utilization and conversion to high-value co-products that can be generated in an integrated biorefinery. Pretreated sweet sorghum bagasse (SSB) was hydrolyzed in sweet sorghum juice (SSJ) followed by ethanol fermentation. Ethanol was removed from the fermentation broth by evaporation to generate a stillage media enriched in xylose. Candida mogii NRRL Y-17032 could easily grow in non-detoxified stillage media, but a high xylitol yield of 0.55 g xylitol/g xylose consumed was achieved after recovered cells were resuspended in synthetic media containing supplemented xylose. Phaffia rhodozyma ATCC 74219 could be cultivated in non-detoxified stillage media, but astaxanthin generation was increased 4-fold (from 17.5 to 71.7 mg/L) in detoxified media. Future processing strategies to boost product output should focus on a two-step process where the stillage media is used as the growth stage, and a synthetic media for the production stage utilizing xylose generated from SSB through selective hemicellulase enzymes.

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Recovered hemicellulose fractions from biorefineries have the potential to improve overall process economics during the production of biofuels or other high value chemicals. A common hemicellulose found in many agricultural feedstocks is arabinoxylan (AX). This work investigated the influence of ferulic and p-coumaric acids on the antioxidant capability of AX hemicellulose recovered from sorghum bran, biomass, and bagasse. Sorghum bagasse and sorghum biomass AX contained the largest quantities of bound ferulic and p-coumaric acids at 13.1 mg/100 g and 6.3 mg/100 g, respectively. Antioxidant performance showed that sorghum bagasse AX hemicellulose produced the best reducing capability, while sorghum biomass and sorghum bran AX hemicellulose performed better as free radical scavengers. A reduction in free radical scavenging, as determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, occurred for sorghum bagasse and sorghum biomass AX hemicellulose at higher polysaccharide concentrations, which was either caused by the solution properties of the AX hemicelluloses or DPPH reaction reversibility in the presence of phenolic compounds with methoxy content. Alternatively, H2O2 scavenging by the AX hemicellulose revealed a dose-dependent response. Although scavenging effect was reduced at higher concentrations, sorghum bagasse AX hemicellulose functioned as having the best antioxidant capacity with respect to total reducing capability.

2,3-butanediol (2,3-BDO) is a platform chemical that can be converted to a wide array of products ranging from bio-based materials to sustainable aviation fuel. This chemical can be produced by a variety of microorganisms in fermentation processes. Challenges remain for high titer 2,3-BDO production during fermentation due to several parameters, but controlling oxygen is one of the most relevant processing parameters to ensure viable product output. This work investigated the fermentation of plant biomass sugars by the 2,3-BDO producer Paenibacillus polymyxa. Aerobic and oxygen limited fermentation conditions were initially evaluated using molasses-based media to determine cell growth and 2,3-BDO output. Similar conditions were then evaluated on hydrolysate from pretreated sweet sorghum bagasse (SSB) that contained fermentable sugars from structural polysaccharides. Fermentations in molasses media under aerobic conditions found that 2,3-BDO could be generated, but over time the amount of 2,3-BDO decreased due to conversion back into acetoin. Oxygen limited fermentation conditions exhibited improved biomass growth, but only limited suppression of 2,3-BDO conversion to acetoin occurred. Glucose depletion appeared to have a greater role influencing 2,3-BDO conversion back into acetoin. Further improvements in 2,3-BDO yields were found by utilizing detoxified SSB hydrolysate.