Influence of dimethyl formamide pulping of wheat straw on cellulose degradation and comparison with Kraft process

The pulping of wheat straw with dimethyl formamide was studied in order to investigate the effects of the cooking variables (temperature (190 degrees C, 200 degrees C, and 210 degrees C) and time (120 min, 150 min, and 180 min) and organic solvent ratio (30%, 50%, and 70%) dimethyl formamide (DMF+water) value) on the degradation of cellulose and degree of polymerization (DP) of organosolv pulp. The SCAN viscosity was applied to estimating the extent of cellulose degradation produced by cooking condition and then, it was compared with Kraft pulp at equal Kappa number. Response of pulp and handsheets properties to the process variables were analyzed using statistical software (MINITAB 14). The process variables (cooking temperature and cooking time) must be set at low variables with high DMF ratio in order to ensure a high yield and high SCAN viscosity. Also, pulps with high mechanical properties can be acceptably obtained at 210 degrees C for 150 min with 50% DMF. Generally, the cooking temperature was a significant factor while the cooking time and DMF ratio had a smaller role. By the comparison of Kraft and organosolv pulp, it can be resulted that DMF basically had improvement role on reducing of cellulose degradation by reason of high SCAN viscosity of organosolv pulp than Kraft pulp under equal kappa number and, scanning electron microscopy (SEM) of obtained pulp. Consequently, the protective action of organic solvent on non-cellulosic polysaccharides of wheat straw against degradation under Kraft pulping conditions was pointed as a main reason of the fairly high yield of organosolv pulps.     

Fractional extraction and physico-chemical characterization of hemicelluloses and cellulose from sugar beet pulp

Four hemicelluloses and cellulose fractions were extracted with 10% KOH or 7.5% NaOH at 15°C for 16 h and with 24% KOH or 17.5% NaOH at 15°C for 2 h from defatted, protein and pectin free, lignified or delignified sugar beet pulp (SBP). There was no significant difference in the yield and sugar composition of isolated hemicelluloses and cellulose obtained from four different procedures. 7.5% NaOH extraction at 15°C for 16 h from lignified SBP gave a slightly higher yield of hemicelluloses (10.96%), while 24% KOH extraction at 15°C for 2 h from delignified SBP produced the highest yield of cellulose (18.35%). Molecular-average weights ranged from 88 850 to 91 330 Da for the hemicelluloses obtained from lignified SBP, and 21 620–21 990 Da for the hemicelluloses isolated from delignified SBP. The neutral sugar composition of the hemicelluloses consisted of glucose, arabinose, galactose, xylose, and minor quantities of rhamnose and mannose. The infrared spectra showed an absorption band at 900 cm⁻¹, indicating some amounts of β-linked polysaccharides. Besides ferulic and p-coumaric acids, six other phenolics were also identified in the mixture of alkaline nitrobenzene oxidation of associated lignin in the isolated hemicelluloses and cellulose fractions.     

Organosolv pulping of wheat straw by use of phenol

A central composite design was used to investigate the influence of the cooking conditions (time, temperature and phenol concentration) for wheat straw with phenol-water mixtures on the properties of the pulp obtained (yield and holocellulose, -cellulose, lignin and ethanol-benzene extractable contents) and the pH of the resulting wastewater. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, -cellulose, lignin and ethanol-benzene extractable contents of the pulp, and the pH of the wastewater with multiple-R, R² and adjusted-R² high values. The process variables must be set at low variables in order to ensure a high yield and pH. Conversely, if high holocellulose and -cellulose contents, and low lignin and ethanol-benzene extractable contents are desired, then a high temperature (200°C), long cooking time (120 min), and intermediate phenol concentration (65%) must be used.     

Temperature and carbon source affect the production and secretion of a thermostable β-xylosidase by Aspergillus fumigatus

The effect of the temperature of growth and carbon source on the production and secretion of β-xylosidase (EC 3.2.1.37) by the thermotolerant fungi Aspergillus fumigatus was studied in submerged cultures. In cultures developed at optimal temperature (30 °C), the enzyme was predominantly cell-bound, while in cultures developed at higher temperature (42 °C), the β-xylosidase activity was predominantly found in the cell-free filtrates. The use of corn cob powder instead of xylan as substrate increased considerably the secretion of enzyme. The highest level of extracellular β-xylosidase (45 U/ml or 360 U/mg protein) was obtained in 3% corn cob cultures grown at 42 °C for 72 h. The partially purified enzyme was active and stable at high temperatures. The presence of high titres of β-xylosidase activity in association with xylanase in the culture filtrates enhanced the efficiency of the pulp hydrolysis process.     

Dilute acid pretreatment, enzymatic saccharification and fermentation of wheat straw to ethanol

Wheat straw consists of 48.57 ± 0.30% cellulose and 27.70 ± 0.12% hemicellulose on dry solid (DS) basis and has the potential to serve as a low cost feedstock for production of ethanol. Dilute acid pretreatment at varied temperature and enzymatic saccharification were evaluated for conversion of wheat straw cellulose and hemicellulose to monomeric sugars. The maximum yield of monomeric sugars from wheat straw (7.83%, w/v, DS) by dilute H₂SO₄ (0.75%, v/v) pretreatment and enzymatic saccharification (45 °C, pH 5.0, 72 h) using cellulase, β-glucosidase, xylanase and esterase was 565 ± 10 mg/g. Under this condition, no measurable quantities of furfural and hydroxymethyl furfural were produced. The yield of ethanol (per litre) from acid pretreated enzyme saccharified wheat straw (78.3 g) hydrolyzate by recombinant Escherichia coli strain FBR5 was 19 ± 1 g with a yield of 0.24 g/g DS. Detoxification of the acid and enzyme treated wheat straw hydrolyzate by overliming reduced the fermentation time from 118 to 39 h in the case of separate hydrolysis and fermentation (35 °C, pH 6.5), and increased the ethanol yield from 13 ± 2 to 17 ± 0 g/l and decreased the fermentation time from 136 to 112 h in the case of simultaneous saccharification and fermentation (35 °C, pH 6.0).     

Extraction of defatted rice bran by subcritical water treatment

Defatted rice bran was treated with subcritical water in the temperature range of 180–280 °C for 5 min using 117 mL and 9 mL vessels to produce the extracts. The total sugar and protein contents and radical scavenging activity of the extracts were then estimated for both vessels. The total sugar concentration of ca. 0.3 g/L-extract was the highest for the extracts at 200 °C, and it significantly decreased at the higher temperatures. The protein concentration and radical scavenging activity were higher at the higher temperatures. Extraction was also done at 200 °C and 260 °C for various times using the small vessel. The total sugar concentration decreased with the increasing extraction time, while the protein concentration and radical scavenging activity only slightly depended on the extraction time. The extracts at 200 °C or lower temperatures using the large vessel possessed the emulsifying and emulsion-stabilizing activities. The HPLC analysis of the extract at 260 °C for 5 min using the small vessel indicated that it contained both hydrophilic and hydrophobic substances. The hydrophilic fraction of the extract mainly contained low-molecular-mass substances.     

Enhancement of albumin secretion by short-term hypothermic incubation of primary rat hepatocytes

A feasibility of hypothermic incubation of hepatocytes as a means of enhancing liver-specific activity was investigated to obtain preferable hepatocytes for a bioartificial liver (BAL) system. Freshly isolated rat hepatocytes were incubated at hypothermic temperatures from 10 to 33 °C for several days, and subsequently cultured at normothermic temperature of 37 °C to evaluate cell viability and albumin secretion activity. The cell viability was decreased by 3-day hypothermic incubations at 10 and 20 °C, while it was maintained even after 3-day hypothermic incubations between 25 and 33 °C. The activity of albumin secretion gradually decreased with prolonging the period of hypothermic incubation at 25 °C. Enhancement of albumin secretion activity was observed in the hypothermic incubations at 30 and 33 °C. The maximum activation of albumin secretion was obtained when hypothermic incubation was performed for 3 days at 30 °C, where the activity increased to 145% of the original activity. The hypothermic incubation at 30 °C also reduced the required time to be the peak of the activity of albumin secretion in the normothermic culture. It was considered that the hypothermic incubation at 30 °C would be effective as a method for pretreatment of isolated hepatocytes for a BAL system.     

Characterisation of thermally modified hard- and softwoods by C CPMAS NMR

The changes induced by thermal modification in the chemical structure of spruce [Picea abies (L.) Karst.], birch (Betula pendula), aspen (Populus tremula) and oak (Quercus robur) were studied by ¹³C CPMAS NMR spectroscopy. Spruce, birch and aspen were thermally modified at 195 °C and oak at 160 °C, under steam, according to an industrial-scale heat treatment process. In both hard- and softwood samples, ¹³C CPMAS NMR measurements revealed a degradation of less ordered carbohydrates (i.e. hemicelluloses and amorphous cellulose) in the thermally modified wood, which resulted in an increase in the cellulose crystallinity. Furthermore, thermal modification induced changes in the lignin structure by a cleavage of the β-O-4 linkages. In the softwood lignin, a decrease also occurred in the methoxyl group content leading to a more condensed lignin structure.     

Characterisation and application of glycanases secreted by Aspergillus terreus CCMI 498 and Trichoderma viride CCMI 84 for enzymatic deinking of mixed office wastepaper

Two enzymatic extracts obtained from xylan-grown Aspergillus terreus CCMI 498 and cellulose-grown Trichoderma viride CCMI 84 were characterised for different glycanase activities. Both strains produce extracellular endoxylanase and endoglucanase enzymes. The enzymes optimal activity was found in the temperature range of 45–60 °C. Endoglucanase systems show identical activity profiles towards temperature, regardless of the strain and inducing substrate. Conversely, the endoxylanases produced by both strains showed maximal activity at different pH values (from 4.5 to 5.5), being the more acidic xylanase produced by T. viride grown on cellulose. The endoglucanase activities have an optimum pH at 4.5–5.0. The endoxylanase and endoglucanase activities exhibited high stability at 50 °C and pH 5.0. Mannanase, β-xylosidase, and amylase activities were also found, being the first two activities only present for T. viride extract. These two enzymatic extracts were used for mixed office wastepaper (MOW) deinking. When the enzymatic extract from T. viride was used, a further increase of 24% in ink removal was obtained by comparison with the control. Both enzymes contributed to the improvement of the paper strength properties and the obtained results clearly indicate that the effective use of enzymes for deinking can also contribute to the pulp and paper properties improvement.     

Recrystallization of waxy maize starch during manufacturing of starch microspheres for drug delivery: Influence of excipients

The formation of ordered structure, such as crystallites, in starch was studied by means of differential scanning calorimetry (DSC). The influence of time/temperature treatment and additives such as polyethylene glycol (PEG), bovine serum albumin (BSA) and a carbonate buffer on the formation was investigated. The experiments were planned with a CCC (Central Composite Circumscribed) design. For all three investigated systems it could be concluded that the incubation time at 6 °C was the decisive factor for the amount of ordered structure obtained during the incubation, while the incubation time at 37 °C was the decisive factor for the thermal stability of the crystallites as expressed by T_on, T_m and T_c. The additives seemed to mainly affect the nucleation phase of crystallization process. The additives decreased the time required in order to obtain a certain level of ordering in the incubated starch samples. The carbonate buffer decreased the amount of ordered structure in starch as judged by DSC enthalpy values, while increasing the melting temperature of these structures. The additives PEG and BSA lowered the melting temperatures of the starch in the systems but increased the enthalpy values. By optimization procedure a specific amount of ordered structure with desired thermal characteristics could be predicted.