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Butanol, produced via traditional acetone-butanol-ethanol (ABE) fermentation, suffers from low yield and productivity. In this article, a non-ABE butanol production process is reviewed. Clostridium pasteurianum has a non-biphasic metabolism, alternatively producing 1,3-propanediol (PDO)-butanol-ethanol, referred to as PBE fermentation. This review discusses the advantages of PBE fermentation with an emphasis on applications using biodiesel-derived crude glycerol, currently an inexpensive and readily available feedstock. To address the process design challenges, various strategies have been employed and are examined and reviewed; genetic engineering and mutagenesis of C. pasteurianum, characterization and pretreatment of crude glycerol and various fermentation strategies such as bioreactor design and configuration, increasing cell density and in-situ product removal. Where research deficiencies exist for PBE fermentation, the process solutions as employed for ABE fermentation are reviewed and their suitability for PBE is discussed. Each of the obstacles against high butanol production has multiple solutions, which are reviewed with the end-goal of an integrated process for continuous high level butanol production and recovery using C. pasteurianum and biodiesel-derived crude glycerol.

In this study, a central composite design and response surface methodology were used to study the effect of various hydrolysis variables (temperature, pH, and time) on the acid hydrolysis of Jerusalem artichokederived inulin using three different mineral acids (HCl, H 2 SO 4 , and H 3 PO 4 ). Numerical optimization was used to maximize the sugar yield of Jerusalem artichoke powder within the experimental range for each of the mentioned acid. The influence of each acid on the formation of hydroxymethylfurfural (HMF; a known by-product and inhibitor for fermentative organisms) was also investigated. H 2 SO 4 was found to have a better potential for sugar yields compared to two other acids (HCl and H 3 PO 4 ) since it can hydrolyze the highest amount of inulin (98.5 %) under optimal conditions (temperature of 97°C, pH of 2.0, and time period of 35 min) without producing inhibiting HMF concentrations. The sulfuric hydrolysate of Jerusalem artichoke was fermented via solventogenic clostridia to acetonebutanol-ethanol (ABE). An ABE yield of 0.31 g g −1 and an overall fermentation productivity of 0.25 g l −1 h −1 were obtained, indicating the suitability of this feedstock for fermentative ABE production.

Bio‐oil from lignocellulosic biomass pyrolysis is a promising feedstock as a precursor for the production of transportation fuels and value‐added chemicals. The presence of significant concentrations of oxygen, water, and acids makes it difficult to use bio‐oil directly as a transportation fuel without costly upgrading. The acidity of pyrolysis liquids is mainly derived from volatile acids, such as acetic acid, causing chemical instability and corrosion. The extraction of acids from bio‐oil can therefore offer strategies for improved applications and economic value. Moreover, acetic acid is a valuable reagent and the building block for several commercially important chemicals. This review presents the results of important research related to the production of bio‐oil‐derived acetic acid. The discussion is intended to summarize the effect of biomass type and pretreatment method, pyrolysis processing conditions, and separation techniques on acetic acid production via pyrolysis. On this basis, acetic acid characterization techniques are also presented along with an overview of acetic acid applications and economic considerations. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd