Non-carbon loss long-term continuous lactic acid production from mixed sugars using thermophilic Enterococcus faecium QU 50

In this study, a non-sterile (open) continuous fermentation (OCF) process with no-carbon loss was developed to improve lactic acid (LA) productivity and operational stability from the co-utilization of lignocellulose-derived sugars by thermophilic Enterococcus faecium QU 50. The effects of different sugar mixtures on LA production were firstly investigated in conventional OCF at 50°C, pH 6.5 and a dilution rate of 0.20 hr⁻¹. The xylose consumption ratio was greatly lower than that of glucose in fermentations with glucose/xylose mixtures, indicating apparent carbon catabolite repression (CCR). However, CCR could be efficiently eliminated by feeding solutions containing the cellobiose/xylose mixture. In OCF at a dilution rate ca. 0.10 hr⁻¹, strain QU 50 produced 42.6 g L⁻¹ of l -LA with a yield of 0.912 g g⁻¹-consumed sugars, LA yield of 0.655 g g⁻¹ based on mixed sugar-loaded, and a productivity of 4.31 g L⁻¹ hr⁻¹ from simulated energy cane hydrolyzate. In OCF with high cell density by cell recycling, simultaneous and complete co-utilization of sugars was achieved with stable LA production at 60.1 ± 3.25 g L⁻¹ with LA yield of 0.944 g g⁻¹-consumed sugar and LA productivity of 6.49 ± 0.357 g L⁻¹ hr⁻¹. Besides this, a dramatic increase in LA yield of 0.927 g g⁻¹ based on mixed sugar-loaded with prolonged operational stability for at least 500 hr (>20 days) was established. This robust system demonstrates an initial green step with a no-carbon loss under energy-saving toward the feasibility of sustainable LA production from lignocellulosic sugars.     

Carbohydrate and lignin contents of plant materials used in animal feeding

A total of 115 samples representing 38 different feedstuffs was analysed for carbohydrates and lignin. The samples were analysed for low-molecular weight (LMW) sugars by high-performance liquid chromatography, starch, fructan and mixed linked β(1 → 3;1 → 4)-D-glucan by colorimetry, total, soluble and insoluble non-starch polysaccharides (NSP) by gas-liquid chromatography and lignin by gravimetry. For all but alfalfa meal, almost quantitative recovery of carbohydrates and lignin was obtained with a deviation between calculated and analysed values of less than 2 g kg⁻¹ dry matter. The correlation between calculated and analysed values was 0.985 (P < 0.0001).The concentration (g kg⁻¹ dry matter) of LMW-sugars varied from 5 g kg⁻¹ and up to 137 g kg⁻¹ with the lowest values found in cereal substitutes, whole grain cereals and by-products while the protein concentrates in general had the highest content of LMW-sugars (57–137 g kg⁻¹). Starch was the main polysaccharide in whole grain cereals where it varied from 468 g kg⁻¹ in oats to 690 g kg⁻¹ in maize, in cereal by-products (93–902 g kg⁻¹) and in tapioca (768 g kg⁻¹). In contrast, the concentration of starch was low in all protein concentrates but peas and faba beans. The lowest levels of NSP and lignin were found in maize flour (NSP, 21 g kg⁻¹; lignin, 4 g kg⁻¹) and the highest levels in oat hull meal (NSP, 503 g kg⁻¹; lignin, 148 g kg⁻¹). There was also a significant variation in NSP and lignin in protein concentrates with the NSP value varying from 189 g kg⁻¹ in faba beans to 451 g kg⁻¹ in white lupins and with lignin varying from 12 g kg⁻¹ in white lupins to 133 g kg⁻¹ in sunflower cake. Grass meal, alfalfa meal and sugar beet fibre had in general high concentrations of NSP and lignin with values in grass and alfalfa meals of NSP: 329–426 g kg⁻¹ and lignin: 128–169 g kg⁻¹ and in sugar beet fibre 779 g kg⁻¹ and 35 g kg⁻¹, respectively.     

Biokraft pulping of European black pine with Ceriporiopsis subvermispora

European black pine (Pinus nigra Arn.) chips were treated with the white-rot fungus Ceriporiopsis subvermispora for periods ranging from 20 to 100 days. The effects of pretreatment on the chemical composition of wood and kraft pulping were investigated. The results showed that fungal pretreatment reduced the lignin and extractive content of wood chips. Also, weight losses occurred. Kappa number, viscosity, and reject ratio of biokraft pulps decreased. Biokraft pulps gave better response to beating, which led to significant energy saving during refining. The tear index, burst index, and tensile index of biokraft pulps were found to be lower than those of kraft pulps. However, the tensile index and burst index of 20-day biotreated and unbeaten pulp was higher than those of kraft pulp. Also, the tear index of 20-day biotreated and beaten pulp was higher than that of kraft pulp. The brightness of biokraft pulps decreased irregularly with increasing incubation time.     

Biorefining of softwoods using ethanol organosolv pulping: preliminary evaluation of process streams for manufacture of fuel-grade ethanol and co-products

Pulps with residual lignin ranging from 6.4-27.4% (w/w) were prepared from mixed softwoods using a proprietary biorefining technology (the Lignol process) based on aqueous ethanol organosolv extraction. The pulps were evaluated for bioconversion using enzymatic hydrolysis of the cellulose fraction to glucose and subsequent fermentation to ethanol. All pulps were readily hydrolyzed without further delignification. More than 90% of the cellulose in low lignin pulps (< or =18.4% residual lignin) was hydrolyzed to glucose in 48 h using an enzyme loading of 20 filter paper units/g cellulose. Cellulose in a high lignin pulp (27.4% residual lignin) was hydrolyzed to >90% conversion within 48 h using 40 filter paper units/g. The pulps performed well in both sequential and simultaneous saccharification and fermentation trials indicating an absence of metabolic inhibitors. Chemical and physical analyses showed that lignin extracted during organosolv pulping of softwood is a suitable feedstock for production of lignin-based adhesives and other products due to its high purity, low molecular weight, and abundance of reactive groups. Additional co-products may be derived from the hemicellulose sugars and furfural recovered from the water-soluble stream.     

Oxalic acid: a microbial metabolite of interest for the pulping industry

Oxalate is a common metabolite produced by almost all plant-pathogenic fungi. The degradation of cell wall from poplar chips and poplar sawdust by oxalate is reviewed here. Oxalate treatments decrease slightly the amount of sugars constituting hemicelluloses, but only in fibres and not in sawdust or wood chips. The examination of the cell wall ultrastructure of wood chips by transmission electron microscopy (TEM) after polysaccharide staining showed a characteristic fading of the staining of the S1/S2 and S2/S3 transition areas, supporting the idea that reactivity and organization of polysaccharides had changed after the oxalate treatments. Finally, all these changes enhanced the ability of the wood chips to be defibrated by a thermomechanical (TMP) process, as well as the further refining of the pulps. Looking at the fiber surface, it became apparent that fracture areas during the TMP pulping had moved toward the S2 layer, explaining why defibrating and refining occurred more easily, with less energy input in the process.     

Enhanced expression of glutamine synthetase (GS1a) confers altered fibre and wood chemistry in field grown hybrid poplar (Populus tremula X alba) (717-1B4)

Hybrid poplar (Populus tremula X P. alba) genetically engineered to express the pine cytosolic glutamine synthetase gene (GS1a) has been previously shown to display desirable field performance characteristics, including enhancements in growth and nitrogen use efficiency. Analysis of wood samples from a 3‐year‐old field trial of three independently transformed GS1a transgenic hybrid poplar lines revealed that, when compared with wild‐type controls, ectopic expression of GS1a resulted in alterations in wood properties and wood chemistry. Included were significant enhancements in wood fibre length, wood density, microfibre angle, per cent syringyl lignin and elevated concentrations of wood sugars, specifically glucose, galactose, mannose and xylose. Total extractive content and acid‐insoluble lignin were significantly reduced in wood of GS1a transgenics when compared with wild‐type trees. Together, these cell wall characteristics resulted in improved wood pulping attributes, including improved lignin solubilization with no concurrent decrease in yield. Trees with increased GS1a expression have improved characteristics for pulp and paper production and hold potential as a feedstock for biofuels production.     

Comparison of industrial yeast strains for fermentation of spent sulphite pulping liquor fortified with wood hydrolysate

Ethanol production from spent sulphite pulping liquor (SSL) was compared for four different yeasts. A second strain of S. cerevisiae as well as a 2-deoxyglucose-resistant strain formed through protoplast fusions between S. uvarum and S. diastaticus produced up to 27% more ethanol from SSL fortified with hydrolysis sugars than was produced by S. cerevisiae. The incremental improvement in ethanol yield appeared to vary with the degree of fortification, ranging from 5.8% for unfortified SSL, to 27% for the highest level of fortification tested. Decreasing fermentation rates were observed for SSL fortified with glucose, mannose and galactose, respectively. Sugar uptake rates in SSL fortified with glucose, galactose and mannose were 6.8, 2.8 and 2.0 g L⁻¹ h⁻¹, respectively. However, when these sugars were fermented along with a glucose cosubstrate, the rate at which the combined glucose/mannose medium was fermented was nearly identical to that of the glucose control. Received 18 April 1996/ Accepted in revised form 27 August 1996     

Evaluation of a combined brown rot decay–chemical delignification process as a pretreatment for bioethanol production from Pinus radiata wood chips

Wood chips of Pinus radiata softwood were biotreated with the brown rot fungus (BRF) Gloeophyllum trabeum for periods from 4 and 12 weeks. Biodegradation by BRF leads to an increase in cellulose depolymerization with increasing incubation time. As a result, the intrinsic viscosity of holocellulose decreased from 1,487 cm³/g in control samples to 783 and 600 cm³/g in 4- and 12-week decayed wood chips, respectively. Wood weight and glucan losses varied from 6 to 14% and 9 to 21%, respectively. Undecayed and 4-week decayed wood chips were delignified by alkaline (NaOH solution) or organosolv (ethanol/water) processes to produced cellulosic pulps. For both process, pulp yield was 5–10% lower for decayed samples than for control pulps. However, organosolv bio-pulps presented low residual lignin amount and high glucan retention. Chemical pulps and milled wood from undecayed and 4-week decayed wood chips were pre-saccharified with cellulases for 24 h at 50°C followed by simultaneous saccharification and fermentation (SSF) with the yeast Saccharomyces cerevisiae IR2-9a at 40°C for 96 h for bioethanol production. Considering glucan losses during wood decay and conversion yields from chemical pulping and SSF processes, no gains in ethanol production were obtained from the combination of BRF with alkaline delignification; however, the combination of BRF and organosolv processes resulted in a calculated production of 210 mL ethanol/kg wood or 72% of the maximum theoretically possible from that pretreatment, which was the best result obtained in the present study.     

Recovery of kraft lignin from pulping wastewater via emulsion liquid membrane process

Kraft lignin (KL) is a renewable source of many valuable intermediate biochemical products currently derived from petroleum. An excessive of lignin comes from pulping wastewater caused an adverse pollution problems hence affecting human and aquatic life. A comprehensive study pertaining to emulsion liquid membrane (ELM) extraction of lignin from pulping wastewater was presented. ELM formulation contains Aliquat 336 as carrier, kerosene as diluent, sodium bicarbonate (NaHCO₃) as stripping agent and Span 80 as surfactant. The emulsion stability was investigated at different surfactant concentrations, homogenizer speed and emulsification time. Modifier (2‐ethyl‐1‐hexanol) was added to avoid segregation of third phase while improving the emulsion stability. At optimum conditions, 95% and 56% of lignin were extracted and recovered, respectively at 10 min of extraction time, 0.007 M of Aliquat 336, 0.1 M of NaHCO₃ and 1:5 of treat ratio. Additional of modifier was contributed to highest recovery up to 98%. The ELM process was found to be equally feasible and quite effective in the recovery of KL from real pulping wastewater. Therefore, ELM process provides a promising alternative technology to recover KL from pulping wastewater while solving the environmental problems simultaneously. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1305–1314, 2015     

Effect of organosolv and soda pulping processes on the metals content of non-woody pulps

In this work the effect of different pulping processes (ethyleneglycol, diethyleneglycol, ethanolamine and soda) of tow abounded raw materials (empty fruit bunches - EFB and rice straw) on the ash, silicates and metals (Fe, Zn, Cu, Pb, Mn, Ni and Cd) content of the obtained pulps have been studied. Results showed that pulps obtained by diethyleneglycol pulping process presented lower metals content (756 microg/g and 501 microg/g for EFB and rice straw pulp, respectively) than soda pulps (984 microg/g and 889 microg/g). Ethanolamine pulps presented values of holocellulose (74% and 77% for EFB and rice straw pulp, respectively), alpha-cellulose (74% and 69%), kappa number (18.7 and 18.5) and viscosity (612 and 90 6ml/g) similar to those of soda pulp, and lower lignin contents (11% and 12%).     

Feasibility of utilizing Rhizoclonium in pulping and papermaking

Material of Rhizoclonium from brackish water in Taiwan was investigated for its possible use in pulping and papermaking. After beating, this filamentous alga produced a pulp with a length to width ratio of about 10, much less than that of a typical wood pulp. Handsheets made from this pulp had a moderate breaking length of 4.02 km. Cooking pre-beaten pulp with a low chemical charge (5–25%NaOH) at a low cooking temperature (100 ^°C), and for a short time (30–120 min) gave high algal pulp yields (70–80%). This cooking process was sulfur-free, but the water requirement was high. After cooking and further caustic soda and bleaching treatments, wide-angle X-ray diffraction and FTIR spectroscopy showed that the crystallinity of the algal pulp increased substantially, but type I cellulose conformation was retained. The best pulp mechanical strengths (breaking length 5.23 km,zero-span tensile strength 79.2 Nm g^-1, bursting index of 2.2 kpa m² g^-1) were obtained after cooking for 1 h with 20% NaOH. Because of the morphological characteristics of the algal strands, the pulp generally lacked bursting, tearing and folding strengths, but proper blending with softwood pulp increased the tensile breaking length to8.40 km, the tearing index to 14.5 mNm² g^-1, the bursting index to 6.42 kpam² g^-1 and the folding endurance to 4299 double folds, i.e. levels comparable to a typical kraft pulp. The algal pulp thus showed clear potential as a supplement for traditional medium strength wood pulps. This revised version was published online in August 2006 with corrections to the Cover Date.     

Oven,Temperature-Controlled Microwave,and Shade Drying Effects on Drying Kinetics,Bioactive Compounds and Antioxidant Activity of Knotweed (Polygonum cognatum Meissn.)

In this study, the plant node was dried in an oven (40, 50 and 60 °C), shade and temperature-controlled microwave (40, 50 and 60 °C) methods. Statistically (p<0.05), the values closest to the color values of fresh grass were determined in an oven at 40 °C drying temperature. Effective diffusion values varied between 8.85×10⁻⁸–5.65×10⁻⁶ m² s⁻¹. While the activation energy was 61.28 kJ mol⁻¹ in the oven, it was calculated as 85.24 kJ mol⁻¹ in the temperature-controlled microwave. Drying data was best estimated in the Midilli-Küçük (R² 0.9998) model oven at 50 °C. The highest SMER value was calculated as 0.0098 kg kWh⁻¹ in the temperature-controlled microwave drying method. The lowest SEC value in the temperature-controlled microwave was determined as 24.03 kWh kg⁻¹. It was determined that enthalpy values varied between −2484.66/−2623.38 kJ mol⁻¹, entropy values between −162.04/−122.65 J mol⁻¹ and Gibbs free energy values between 453335.22–362581.40 kJ mol⁻¹. Drying rate values were calculated in the range of 0.0127–0.9820 g moisture g dry matter⁻¹ in the temperature-controlled microwave, 0.0003–0.0762 g dry matter⁻¹ in the oven, and 0.001–0.0058 g moisture g dry moisture matter⁻¹ in the shade. Phenolic content 6957.79 μg GAE g⁻¹ fw - 48322.27 μg GAE g⁻¹ dw, flavonoid content 3806.67 mg KE L⁻¹ fw - 22200.00 mg KE L⁻¹ dw and antioxidant capacity 43.35 μmol TE g⁻¹ fw - 323.47 μmol TE g⁻¹ dw. The highest chlorophyll values were obtained from samples dried in an oven at 40 °C. According to the findings, it is recommended to dry the knotweed (Polygonum cognatum Meissn.) plant in a temperature-controlled microwave oven at low temperatures. In this study, in terms of drying kinetics and energy parameters, a temperature-controlled microwave dryer of 60 °C is recommended, while in terms of quality characteristics, oven 40 °C and shade methods are recommended.     

Butanol production from wheat straw hydrolysate using <Emphasis Type="Italic">Clostridium beijerinckii</Emphasis>

In these studies, butanol (acetone butanol ethanol or ABE) was produced from wheat straw hydrolysate (WSH) in batch cultures using Clostridium beijerinckii P260. In control fermentation 48.9 g L⁻¹ glucose (initial sugar 62.0 g L⁻¹) was used to produce 20.1 g L⁻¹ ABE with a productivity and yield of 0.28 g L⁻¹ h⁻¹ and 0.41, respectively. In a similar experiment where WSH (60.2 g L⁻¹ total sugars obtained from hydrolysis of 86 g L⁻¹ wheat straw) was used, the culture produced 25.0 g L⁻¹ ABE with a productivity and yield of 0.60 g L⁻¹ h⁻¹ and 0.42, respectively. These results are superior to the control experiment and productivity was improved by 214%. When WSH was supplemented with 35 g L⁻¹ glucose, a reactor productivity was improved to 0.63 g L⁻¹ h⁻¹ with a yield of 0.42. In this case, ABE concentration in the broth was 28.2 g L⁻¹. When WSH was supplemented with 60 g L⁻¹ glucose, the resultant medium containing 128.3 g L⁻¹ sugars was successfully fermented (due to product removal) to produce 47.6 g L⁻¹ ABE, and the culture utilized all the sugars (glucose, xylose, arabinose, galactose, and mannose). These results demonstrate that C. beijerinckii P260 has excellent capacity to convert biomass derived sugars to solvents and can produce over 28 g L⁻¹ (in one case 41.7 g L⁻¹ from glucose) ABE from WSH. Medium containing 250 g L⁻¹ glucose resulted in no growth and no ABE production. Mixtures containing WSH + 140 g L⁻¹ glucose (total sugar approximately 200 g L⁻¹) showed poor growth and poor ABE production. Mention of trade names or commercial products in this article is solely for the purpose of providing scientific information and does not imply recommendation or endorsement by the United States Department of Agriculture.     

Continuous acetone-butanol-ethanol fermentation using SO2-ethanol-water spent liquor from spruce

SO₂–ethanol–water (SEW) spent liquor from spruce chips was successfully used for batch and continuous production of acetone, butanol and ethanol (ABE). Initially, batch experiments were performed using spent liquor to check the suitability for production of ABE. Maximum concentration of total ABE was found to be 8.79 g/l using 4-fold diluted SEW liquor supplemented with 35 g/l of glucose. The effect of dilution rate on solvent production, productivity and yield was studied in column reactor consisting of immobilized Clostridium acetobutylicum DSM 792 on wood pulp. Total solvent concentration of 12 g/l was obtained at a dilution rate of 0.21 h⁻¹. The maximum solvent productivity (4.86 g/l h) with yield of 0.27 g/g was obtained at dilution rate of 0.64 h⁻¹. Further, to increase the solvent yield, the unutilized sugars were subjected to batch fermentation.     

Delignification of Wood Chips and Pulps by Using Natural and Synthetic Porphyrins: Models of Fungal Decay

Kraft pulps, prepared from softwoods, and small chips of birch wood were treated with heme and tert-butyl hydroperoxide in aqueous solutions at reflux temperature. Analyses of treated pulps showed decreases in kappa number (a measure of lignin content) from about 36 to less than 2, with concomitant increases in brightness (80% increase in the better samples). Analyses of treated wood chips revealed selective delignification and removal of hemicelluloses. After 48 h of treatment, lignin losses from the wood chips approached 40%, and xylose/mannose (hemicellulose) losses approached 70%, while glucose (cellulose) losses were less than 10%. Examination of delignified chips by transmission electron microscopy showed that the removal of lignin occurred in a manner virtually indistinguishable from that seen after decay by white rot fungi. Various metalloporphyrins, which act as biomimetic catalysts, were compared to horseradish peroxidase and fungal manganese peroxidase in their abilities to oxidize syringaldazine in an organic solvent, dioxane. The metalloporphyrins and peroxidases behaved similarly, and it appeared that the activities of the peroxidases resulted from the extraction of heme into the organic phase, rather than from the activities of the enzymes themselves. We concluded that heme-tert-butyl hydroperoxide systems in the absence of a protein carrier mimic the decay of lignified tissues by white rot fungi.     

Predicting the most appropriate wood biomass for selected industrial applications: comparison of wood,pulping, and enzymatic treatments using fluorescent-tagged carbohydrate-binding modules

Background

Lignocellulosic biomass will progressively become the main source of carbon for a number of products as the Earth’s oil reservoirs disappear. Technology for conversion of wood fiber into bioproducts (wood biorefining) continues to flourish, and access to reliable methods for monitoring modification of such fibers is becoming an important issue. Recently, we developed a simple, rapid approach for detecting four different types of polymer on the surface of wood fibers. Named fluorescent-tagged carbohydrate-binding module (FTCM), this method is based on the fluorescence signal from carbohydrate-binding modules-based probes designed to recognize specific polymers such as crystalline cellulose, amorphous cellulose, xylan, and mannan.

Results

Here we used FTCM to characterize pulps made from softwood and hardwood that were prepared using Kraft or chemical-thermo-mechanical pulping. Comparison of chemical analysis (NREL protocol) and FTCM revealed that FTCM results were consistent with chemical analysis of the hemicellulose composition of both hardwood and softwood samples. Kraft pulping increased the difference between softwood and hardwood surface mannans, and increased xylan exposure. This suggests that Kraft pulping leads to exposure of xylan after removal of both lignin and mannan. Impact of enzyme cocktails from Trichoderma reesei (Celluclast 1.5L) and from Aspergillus sp. (Carezyme 1000L) was investigated by analysis of hydrolyzed sugars and by FTCM. Both enzymes preparations released cellobiose and glucose from pulps, with the cocktail from Trichoderma being the most efficient. Enzymatic treatments were not as effective at converting chemical-thermomechanical pulps to simple sugars, regardless of wood type. FTCM revealed that amorphous cellulose was the primary target of either enzyme preparation, which resulted in a higher proportion of crystalline cellulose on the surface after enzymatic treatment. FTCM confirmed that enzymes from Aspergillus had little impact on exposed hemicelluloses, but that enzymes from the more aggressive Trichoderma cocktail reduced hemicelluloses at the surface.

Conclusions

Overall, this study indicates that treatment with enzymes from Trichoderma is appropriate for generating crystalline cellulose at fiber surface. Applications such as nanocellulose or composites requiring chemical resistance would benefit from this enzymatic treatment. The milder enzyme mixture from Aspergillus allowed for removal of amorphous cellulose while preserving hemicelluloses at fiber surface, which makes this treatment appropriate for new paper products where surface chemical responsiveness is required.

     

Biodegradation of Lignocellulose by White-Rot Fungi: Structural Characterization of Water-Soluble Hemicelluloses

In the biological pretreatment process, white-rot fungi are mostly used to degrade lignin and carbohydrates in lignocellulosic biomass. In this study, water-soluble hemicelluloses were recovered from birch wood (Betula alnoides) decayed by white-rot fungi (Ganoderma lucidum C7016) for different durations up to 16 weeks. Accordingly, the dimethyl sulfoxide (DMSO)-soluble hemicelluloses were isolated from the untreated birch wood as a comparison. Results showed that the fungal-degraded polysaccharides were acidic hemicelluloses having a high content of uronic acids ranging from 20.6 to 22.5 %. Gel permeation chromatography analysis demonstrated that the recovered water-soluble hemicelluloses had a lower average molecular weight (M _w, 15,990–27,560 g?mol^?1) than that of the DMSO-soluble hemicelluloses (M _w , 33,960 g?mol^?1). Fourier transform infrared spectroscopy, scanning electron microscopy, one- and two-dimensional nuclear magnetic resonance spectroscopy also revealed significantly changes between those of fungal degraded and DMSO-soluble hemicelluloses. It was proposed that the hemicelluloses with low molecular weights were easily removed from wood by fungal degradation. This research revealed the changes of hemicelluloses in fungal degradation in the natural environment, which may enable the exploration of novel methods in bioconversion of lignocellulosic biomass for the production of biofuels and biopolymers, in addition to the development of new and better ways to protect wood from biodegradation by microorganisms.     

Partitioning of amylase produced by Aspergillus niger in solid state fermentation using aqueous two-phase systems

Equilibrium data of aqueous two-phase systems composed of polyethylene glycol (4000 g mol⁻¹ or 6000 g mol⁻¹) and Li₂SO_4, (NH₄)₂SO₄ or Na₂SO₄ at pH 6.5 and 25 °C were obtained. The efficiency of these in the partition of amylases derived from Aspergillus niger was determined. The experimental data of binodal curves and tie lines were used to estimate the group interaction parameters using the UNIFAC model. Additionally, the influence of phases on the activity of the enzymes was investigated. The results indicate that the polymer molar mass did not influence the biphasic region size. However, the cations under study presented differences in induction to phase formation. It was verified that the systems formed with the Na⁺ presented a larger biphasic region. The increase in the molar mass of the polymer caused the increase in the exclusion volume from 3970.732 g mol⁻¹ to 5700.873 g mol⁻¹. The transfer Gibbs free energy of enzymes presented values between −1296.30 kJ mol⁻¹ and −2867.70 kJ mol⁻¹, that is, the process was spontaneous for all systems studied. The systems formed by (NH₄)₂SO₄ and PEG 4000 g mol⁻¹ presented the best K_e result (3.421) and theoretical recovery of 80.35 %.     

Effect of pulping variables with dimethyl formamide on the characteristics of bagasse-fiber

Organosolv pulping of bagasse was conducted following a central composite design using a two-level factorial plan involving three pulping variables (temperature: 190-210 degrees C, time: 120-180 min, organic solvent ratio: 40-60% dimethyl formamide). Responses of pulp and handsheets properties to the process variables were analyzed using statistical software (MINITAB 14). Using values of the independent variables the variation ranges considered provided the following optimum values of the dependent variables: 82.7% (yield), 92.9 (kappa number), 1.403% (ash), 370 ml (freeness), 6290 m (breaking length), 9.4 (folding endurance), 5.955 mN m2 g(-1) (Tear index) and 2.811 kN g(-1) (Burst index) for pulps and handsheets. Results showed that acceptable physical and mechanical properties of pulps and papers similar the pulp used for bleaching could be achieved at 210 degrees C for 150 min and 50% DMF. These are the most suitable conditions for obtaining paper sheets with a high breaking length, tear and burst indices. Also bagasse could be pulped with ease to about 55.72% yield with kappa number approximately 35. The cooking temperature was a significant factor while the DMF ratio and cooking time were not as important in term of the properties of the resultant pulps and papers.     

Impact of fly ash pretreatment on aerobic treatment of thermomechanical pulping spent liquor

This study investigated the impact of biomass‐based fly ash (FA) pretreatment on the biodegradability of a thermomechanical pulping spent liquor (TMPL) in an aerobic system. In this study, FA was mixed with TMPL under the conditions of 6 wt.% based on TMPL, 25°C and 10 h, which removed a part of recalcitrant organic materials and resulted in 68.0, 40.0, 60.1, 81.2 and 48.3% reductions in chemical oxygen demand (COD), biochemical oxygen demand (BOD), total organic carbon (TOC), lignin and sugar, respectively. FA‐pretreated TMPL pressate (FA‐TMPL) was biologically treated in an aerobic system of sequencing batch reactor (SBR). The performance of the biological treatment with and without FA pretreatment was studied in two parallel SBRs over three months. The combination of FA and biological treatments removed 97.3% of COD, 98.3% of BOD, 96.3% of lignin, 99.5% of sugar, and 98.1% of TOC. Without FA pretreatment, the biological system removed 87.3% of COD, 89% of BOD, 81.6% of lignin, 98.6% of sugars, and 90.5% of TOC. The results also confirmed that the settling ability of sludge, which was indicated as a sludge volume index, was reduced from 109.3 mL/g to 53.5 mL/g. In addition, the advantages of using FA pretreatment in aerobic systems were discussed in detail. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:370–378, 2018