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Highlights • Use of Southern Pine wood sugars is demonstrated for production of solvents. • Fermentation of C6 and C5-rich streams is shown with productivity above 10 g/L/h. • Membrane assisted continuous fermentation is demonstrated for solvent production. • Use of butyl butyrate as an extractant for solvent extraction demonstrated. • Raffinate after solvent extraction was recycled back without any toxicity issues. Abstract The aim of this work was to demonstrate an industrially relevant pilot scale integrated process to produce butanol and other solvents from lignocellulosic sugars produced with AVAP® biomass fractionation technology from southern pine wood. The concentrated sugars were concurrently fermented using genetically engineered Clostridium acetobutylicum to n-butanol, acetone, isopropanol and ethanol in continuous membrane assisted cell recycle fermentation with steady-state solvent productivity exceeding 10 g/L/h. The solvents from the cell free permeate were recovered with extractant of butyl butyrate in a continuous liquid-liquid extraction column and aqueous product (raffinate) along with unused sugars, nutrients, and metabolic intermediates were recycled back to the fermentors. The total solvent yield approached 0.30 g/g sugars. [ABSTRACT FROM AUTHOR]

• Waste wood is converted to sugars and ethanol on a pilot scale with SO 2 -ethanol-water. • SO 2 -ethanol-water pretreatment of waste wood results in high sugar yields. • Pilot scale sugar yields matched earlier laboratory scale results. Two grades of recycled wood (Waste Wood A and Waste Wood B) were fractionated on a pilot scale (800 BD kg) to monomeric sugars, lignin and lignosulfonates using SO 2 -Ethanol-Water (AVAP®) technology, including pretreatment, separation of cellulosic and hemicellulosic streams, and saccharification. Carbohydrate mass balance was obtained through determination of poly-, oligo- and monosaccharides as well as sugar degradation products in process streams. High monosaccharide yields were obtained confirming laboratory scale findings. Fermentability of mixed cellulosic and hemicellulosic sugar stream was confirmed on bench scale (25 kg). [ABSTRACT FROM AUTHOR]

• Recycled wood is converted to monosugars, lignin and lignosulfonates with SO 2 -ethanol. • SO 2 -ethanol converts recycled wood to digestible cellulose and fermentable sugars. • SO 2 -ethanol process produces monosugars at ~560–610 kg per BD ton recycled wood. • SO 2 -ethanol process produces lignin at ~150–155 kg per BD ton recycled wood. Recycled wood of two grades (A and B) and spruce were converted on bench (100 o.d. g) and pilot (100 o.d. kg) scales to monosugars, lignin and lignosulfonates using SO 2 -Ethanol-Water (AVAP®) technology. After digestion, C6 and C5 sugars were recovered at 98–100% and 87–99% for Wood A and Spruce, respectively, while the values for Wood B were 92% and 74–87%. Cellulose was hydrolysed to glucose at 90% or higher using enzyme charge of 7.1 FPU/g glucan. Hemicellulosic sugars were autohydrolyzed to 95–100% monosugars. At bench scale, monosaccharide yield was 609, 561 and 688 kg (hydrous) per BDT biomass for Wood A, Wood B and Spruce, respectively. Corresponding water insoluble lignin yield was 157, 148 and 189 kg per BDT biomass. The preliminary techno-economic evaluation revealed that conversion of recycled wood to sugars using AVAP® fractionation platform results in higher profitability in comparison to virgin wood. [ABSTRACT FROM AUTHOR]

Acetone being a non-fuel solvent produced during the traditional acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum ; reduces the overall fuel alcohol yield. However, the conversion of acetone into isopropanol has been recommended to improve the process economy. The present study aims to develop an engineered C. acetobutylicum DSM 792 strain to convert acetone into isopropanol by introducing the secondary alcohol dehydrogenase gene from Clostridium beijerinckii NRRL B593 using the allele-coupled exchange approach. Batch and continuous fermentation experiments were carried out with a modified strain C. acetobutylicum DSM 792-ADH to improve the isopropanol yield and titer. The growth and production behavior of the modified strain in stationary flask culture and controlled batch culture was studied. Almost 50% of acetone was converted into isopropanol with highest total solvent yield to be 0.39 g g −1 glucose. The modified strain also utilized sugar mixture and SO 2 –ethanol–water spent liquor as a substrate to produce the solvents. [ABSTRACT FROM AUTHOR]

The co-production of acetone during traditional butanol fermentation (acetone–butanol–ethanol) lowers the yield of alcohol biofuels. The present study was aimed to develop an improved Clostridium acetobutylicum strain with enhanced alcohol fuel production capability. The previously developed IBE (isopropanol-butanol-ethanol) producing C. acetobutylicum DSM792-ADH strain was further optimized to enhance the solvent productivity and yield. Immobilized cell column reactor was used to investigate the effect of dilution rate on IBE fermentation. Pure glucose, artificial sugar mixture and SEW spent liquor from spruce chips were used as substrates to study the behavior of the modified microorganism. The highest total solvent concentrations of approximately 10.60 g l −1 , 10 g l −1 and 6 g l −1 were obtained when glucose, sugar mixture and SEW spent liquor were used as substrates respectively. The modified microorganism could effectively utilize the lignocellulosic biomass hydrolyzate (SEW spent liquor) to yield a solvent productivity of 1.67 g l −1 h −1 . [ABSTRACT FROM AUTHOR]

The biomass obtained after the extraction of forskolin from the roots of Coleus forskohlii was evaluated as a substrate for the production of acetone-butanol-ethanol (ABE). The spent biomass constituting more than 90% of the raw material showed 50–70% carbohydrates with starch and cellulose being the major constituents. This study was undertaken to optimize enzymatic hydrolysis of C. forskohlii roots for maximum release of fermentable sugars and subsequent fermentation to ABE. The root biomass was hydrolyzed using the Stargen ® 002 and Accellerase ® 1500. Cocktail of both enzymes (16U Stargen ® 002 and 60 FPU Accellerase ® 1500) could produce 41.2 g/l of total reducing sugars (glucose equivalent to 32.33 g/l). The production of ABE was optimized in a batch fermentation using Clostridium acetobutylicum NCIM 2877. The maximum ABE production using the root hydrolysates was 0.55 g/l. Pretreatment with lime and Amberlite XAD-4 increased the production of total solvent to 5.33 g/l. [ABSTRACT FROM AUTHOR]

In a previous study by the authors, it was found that benzene-ethanol extraction (BAE) could remove some of the lignin fragments from pretreated bamboo substrate and therefore cause a decrease in the lignin content of the substrate. In the present study, lignin was isolated by dioxane extraction of enzyme hydrolysis of ball-milled substrate (CEL method), and the effects of BAE on lignin molecular weight (MW) were determined. Results indicated that hydrothermal pretreatment could facilitate lignin isolation substantially when CEL method was used. Lignin fragments with low MW were more sensitive to BAE, and therefore, evident increase in both weight average molecular weight (Mw) and number average molecular weight (Mn) was observed; especially, the increase rate of Mn was more than 2.5 times of Mw when degradation prevailed. However, subtle changes were found in Fourier transform infrared spectroscopy and carbon-13 nuclear magnetic resonance spectra between the lignin samples with and without BAE; the solubility of lignin in benzene-ethanol solution was more dependent on the MW level than on the functional groups in lignin structure. [ABSTRACT FROM AUTHOR]

Alcohol dehydrogenase was covalently conjugated with three different oxidized carbohydrates i.e., glucose, starch and pectin. All the carbohydrates inhibited the enzyme. The inhibition was studied with respect to the inhibition rate constant, involvement of thiol groups in the binding, and structural changes in the enzyme. The enzyme activity decreased to half of its original activity at the concentration of 2 mg/mL of pectin, 4 mg/mL of glucose and 10 mg/mL of starch within 10 min at pH 7. This study showed oxidized pectin to be a potent inhibitor of alcohol dehydrogenase followed by glucose and starch. Along with the aldehyde-amino group interaction, thiol groups were also involved in the binding between alcohol dehydrogenase and carbohydrates. The structural changes occurring on binding of alcohol dehydrogenase with oxidized carbohydrates was also confirmed by fluorescence spectrophotometry. Oxidized carbohydrates could thus be used as potential inhibitors of alcohol dehydrogenase. [ABSTRACT FROM AUTHOR]

Non-covalent interaction of alcohol dehydrogenase with polysaccharides was studied using three neutral and three anionic polysaccharides. The process of interaction of alcohol dehydrogenase with gum Arabic was optimized with respect to the ratio of enzyme to gum Arabic, pH, and molarity of buffer. Alcohol dehydrogenase-gum Arabic complex formed under optimized conditions showed 93 % retention of original activity with enhanced thermal and pH stability. Lower inactivation rate constant of alcohol dehydrogenase-gum Arabic complex within the temperature range of 45 to 60 °C implied its better stability. Half-life of alcohol dehydrogenase-gum Arabic complex was higher than that of free alcohol dehydrogenase. A slight increment was observed in kinetic constants ( K and V) of gum Arabic-complexed alcohol dehydrogenase which may be due to interference by gum Arabic for the binding of substrate to the enzyme. Helix to turn conversion was observed in complexed alcohol dehydrogenase as compared to free alcohol dehydrogenase which may be responsible for observed stability enhancement. [ABSTRACT FROM AUTHOR]