Increasing the Production of Volatile Fatty Acids from Corn Stover Using Bioaugmentation of a Mixed Rumen Culture with Homoacetogenic Bacteria.

Volatile fatty acids (VFA) are industrially versatile chemicals and have a major market. Although currently produced from petrochemicals, chemical industries are moving towards more bio-based VFA produced from abundant, cheap and renewable sources such as lignocellulosic biomass. In this study, we examined the effect of bioaugmentation with homoacetogenic bacteria for increasing VFA production in lignocellulose fermentation process. The central hypothesis of this study was that inhibition of methanogenesis in an in vitro rumen bioreactor fed with lignocellulosic biomass hydrolysate increases the hydrogen partial pressure, which can be redirected towards increased VFA production, particularly acetic acid, through targeted bioaugmentation with known homoacetogenic bacteria. In this study, methanogenesis during ruminal fermentation of wet exploded corn stover was initially inhibited with 10 mM of 2-bromoethanesulfonate (BES), followed by bioaugmentation with either Acetitomaculum ruminis and Acetobacterium woodii in two separate bioreactors. During the inhibition phase, we found that addition of BES decreased the acetic acid yield by 24%, while increasing headspace hydrogen from 1% to 60%. After bioaugmentation, the headspace hydrogen was consumed in both bioreactors and the concentration of acetic acids increased 45% when A. ruminis was added and 70% with A. woodii added. This paper demonstrates that mixed microbial fermentation can be manipulated to increase VFA production through bioaugmentation.

Rheology of Polyacrylonitrile/Lignin Blends in Ionic Liquids under Melt Spinning Conditions.

Lignin, while economically and environmentally beneficial, has had limited success in use in reinforcing carbon fibers due to harmful chemicals used in biomass pretreatment along with the limited physical interactions between lignin and polyacrylonitrile (PAN) during the spinning process. The focus of this study is to use lignin obtained from chemical-free oxidative biomass pretreatment (WEx) for blending with PAN at melt spinning conditions to produce carbon fiber precursors. In this study, the dynamic rheology of blending PAN with biorefinery lignin obtained from the WEx process is investigated with the addition of 1-butyl-3-methylimidazolium chloride as a plasticizer to address the current barriers of developing PAN/lignin carbon fiber precursors in the melt-spinning process. Lignin was esterified using butyric anhydride to reduce its hydrophilicity and to enhance its interactions with PAN. The studies indicate that butyration of the lignin (BL) increased non-Newtonian behavior and decreased thermo-reversibility of blends. The slope of the Han plot was found to be around 1.47 for PAN at 150 °C and decreased with increasing lignin concentrations as well as temperature. However, these blends were found to have higher elasticity and solution yield stress (47.6 Pa at 20%wt BL and 190 °C) when compared to pure PAN (5.8 Pa at 190 °C). The results from this study are significant for understanding lignin-PAN interactions during melt spinning for lower-cost carbon fibers.

Characterization of coffee (Coffea arabica) husk lignin and degradation products obtained after oxygen and alkali addition.

The full use of biomass in future biorefineries has stimulated studies on utilization of lignin from agricultural crops, such as coffee husk, a major residue from coffee processing. This study focuses on characterizing the lignin obtained from coffee husk and its further wet oxidation products as a function of alkali loading, temperature and residence time. The lignin fraction after diluted acid and alkali pretreatments is composed primarily of p-hydroxylphenyl units (≥49%), with fewer guaiacyl and syringyl units. Linkages appear to be mainly ß-O-4 ether linkages. Thermal degradation of pretreated lignin during wet oxidation occurred in two stages. Carboxylic acids were the main degradation product. Due to the condensed structure of this lignin, relatively low yields of aromatic aldehydes were achieved, except with temperatures over 210 °C, 5 min residence time and 11.7 wt% NaOH. Optimization of the pretreatment and oxidation parameters are important to maximizing yield of high-value bioproducts from lignin.

Anaerobic digestion of organic fraction from hydrothermal liquefied algae wastewater byproduct.

The wastewater stream from hydrothermal liquefaction (HTL) process used in biofuel production, contains a large amounts of organic compounds where several can be regarded as environmentally hazardous and requires significant treatment before disposal. In this study, semi-continuous anaerobic digestion is used to degrade the organic fraction of wastewater streams from HTL of the algae Tetraselmis (AgTet) and Chlorella (AgChlr). Results indicated high methane yields at 20-30% (v/v) HTL wastewater together with clarified manure, producing 327.2mL/gVSin (or volatile solids in feed) for AgTet and 263.4mL/gVSin for AgChlr. There was a significant reduction in methane production at concentrations higher than 40% (v/v) HTL wastewater in the feed, possibly due to the accumulation of chloride salts or inhibitory compounds such as pyridines, piperidines and pyrrolidines. This was further confirmed by comparing COD, salt and the ammonia concentrations of the effluents after anaerobic digestion at different concentrations of wastewater in manure.

Oxidative degradation of biorefinery lignin obtained after pretreatment of forest residues of Douglas Fir.

Harvested forest residues are usually considered a fire hazards and used as "hog-fuel" which results in air pollution. In this study, the biorefinery lignin stream obtained after wet explosion pretreatment and enzymatic hydrolysis of forestry residues of Douglas Fir (FS-10) was characterized and further wet oxidized under alkaline conditions. The studies indicated that at 10% solids, 11.7wt% alkali and 15min residence time, maximum yields were obtained for glucose (12.9wt%), vanillin (0.4wt%) at 230°C; formic acid (11.6wt%) at 250°C; acetic acid (10.7wt%), hydroxybenzaldehyde (0.2wt%), syringaldehyde (0.13wt%) at 280°C; and lactic acid (12.4wt%) at 300°C. FTIR analysis of the solid residue after wet oxidation showed that the aromatic skeletal vibrations relating to lignin compounds increased with temperature indicating that higher severity could result in increased lignin oxidation products. The results obtained, as part of the study, is significant for understanding and optimizing processes for producing high-value bioproducts from forestry residues.

Design and optimization of a semicontinuous hot-cold extraction of polyphenols from grape pomace.

Grape pomace contains appreciable amounts of polyphenolic compounds such as anthocyanins and procyanidins which can be recovered for use as food supplements. The extraction of these polyphenols from the pomace is usually accomplished at slightly elevated temperatures, frequently employing hydroethanolic solvents. Due to governmental regulations and the cost involved in using ethanol as a solvent, as well as the loss in polyphenolics due to thermal degradation, improved extraction techniques are required. In this study, a semicontinuous extraction apparatus employing only water was developed to maximize the recovery of anthocyanins and procyanidins from red grape pomace (Vitis vinifera). Water is preheated prior to its entry to the extraction cell containing the grape pomace sample, where it is allowed to then flow continuously through the unheated extraction vessel prior to its collection at ambient conditions. Extraction variables that impacted the polyphenolic recovery included pomace moisture content (crude or dried), sample mass, water flow rate, and extraction temperature. A response surface method was used to analyze the results from the extraction, and the optimal conditions were found to be 140 °C and 9 mL/min water flow rate. These conditions can produce an extract containing 130 mg/100 g DW of anthocyanins and 2077 mg/100 g DW of procyanidins. Higher yields of polyphenolics were observed using crude (wet) rather than dried pomace, hence avoiding the need to dry the pomace prior to extraction. The described semicontinuous extraction method using only water as the extraction solvent under subcritical conditions allowed the efficient extraction of polyphenols from red grape pomace without the attendant loss of polyphenolic content due to having to heat the extraction vessel prior to commencement of extraction.

Subcritical solvent extraction of anthocyanins from dried red grape pomace.

Accelerated solvent extraction (ASE) was used to optimize and determine the effectiveness of an alternative, environmentally friendly extraction procedure using subcritical solvents to recover anthocyanins from freeze-dried, ground Sunbelt red grape pomace. Anthocyanins were extracted from pomace using the following ASE variables: pressure (6.8 MPa), one extraction cycle, and temperature (40, 60, 80, 100, 120, and 140 degrees C). Conventional solvent extraction with methanol/water/formic acid (60:37:3 v/v/v) was compared to four hydroethanolic solvents (10, 30, 50, and 70% ethanol in water, v/v). Anthocyanins in the extracts were identified and quantified by HPLC-MS and HPLC. There was an insignificant interaction between solvent and temperature (p = 0.0663). Solvents containing 70 and 50% ethanol in water extracted more total anthocyanins (463 and 455 mg/100 g of DW, respectively) than other solvents. The total amounts of anthocyanins extracted at 100 degrees C (450 mg/100 g of DW), 80 degrees C (436 mg/100 g of DW), and 120 degrees C (411 mg/100 g of DW) were higher than at the other temperatures. Solvents containing 70 and 50% ethanol in water extracted similar amounts of anthocyanins as conventional extraction solvent.

Subcritical solvent extraction of procyanidins from dried red grape pomace.

Procyanidins in dried Sunbelt ( Vitis labrusca L.) red grape pomace were extracted using accelerated solvent extraction (ASE) with pressure (6.8 MPa), one extraction cycle, and temperature (40, 60, 80, 100, 120, and 140 degrees C). Six ethanol/water solvents (0, 10, 30, 50, 70, and 90%, v/v) were compared to conventional extraction with acetone/water/acetic acid (70:29.5:0.5, v/v/v). Procyanidins in the extracts were identified by HPLC-ESI-MS/MS and contained degrees of polymerization (DP) of 1-5 (monomers through pentamers) and polymers (DP > 10). Generally, 50% ethanol/water (v/v) extracted more total procyanidins than other ethanol/water compositions, and contained up to 115% of total procyanidins extracted by the acetone-based conventional solvent. Additionally, 50% ethanol/water (v/v) extracted 205, 221, and 113% more epicatechin, catechin, and dimers, respectively, than conventional extraction. Results indicated greater extraction of low oligomeric procyanidins using 50% ethanol/water (v/v) solvent between 80 and 140 degrees C.