Bioethanol production from sweet sorghum bagasse by Mucor hiemalis

The present work deals with production of ethanol from sweet sorghum bagasse by a zygomycetes fungus Mucor hiemalis. The bagasse was treated with phosphoric acid and sodium hydroxide, with or without ultrasonication, prior to enzymatic hydrolysis by commercial cellulase and β-glucosidase enzymes. The phosphoric acid pretreatment was performed at 50 °C for 30 min, while the alkali treatment performed with 12% NaOH at 0 °C for 3 h. The pretreatments resulted in improving the subsequent enzymatic hydrolysis to 79-92% of the theoretical yield. The best hydrolysis performance was obtained after pretreatment by NaOH assisted with ultrasonication. The fungus showed promising results in fermentation of the hydrolyzates. In the best case, the hydrolyzate of NaOH-ultrasound pretreated bagasse followed by 24 h fermentation resulted in about 81% of the corresponding theoretical ethanol yield. Furthermore, the highest volumetric ethanol productivity was observed in the hydrolyzates of NaOH pretreated bagasse, especially after ultrasonication in pretreatment stage.     

Impact of aggregate coating with a PEC elastomer on properties of lightweight flax shive concrete

Lightweight concrete becomes an important subject of research because of its insulating properties. The main objective of this research is to present a process improving the flax shive behaviour in a cement matrix. Flax shives stem from flax culture. It is the major product (50% of biomass weight). To be used as aggregates, shives should have a hydrophobization treatment. The aim of this work is the treatment of shives with a biodegradable elastomer: poly(PEG-co-CA). This elastomer is synthesized by the polycondensation of polyethylenglycol (PEG) and citric acid (CA). After their treatment with PEC elastomer, flax shives show a decrease in water absorption. Then, they are incorporated in a cement matrix. Mechanical properties, thermal properties and behaviour towards water (dimensional variations) of concrete are determined. The shive treatment shows an improvement in compressive and flexural strengths but an increase in thermal conductivity. The extreme dimensional variations (EDVs) and drying shrinkage (DS) decrease also with concrete prepared with treated shives compared to the standard. Overall the lightweight concrete obtained exhibits performances close to those of wood concrete.     

Susceptibility of wheat gluten to enzymatic hydrolysis following deamidation with acetic acid and sensory characteristics of the resultant hydrolysates

The effect of acetic acid and hydrochloric acid (HCl) deamidation pretreatment on the susceptibility of wheat gluten to enzymatic hydrolysis by Pancreatin and sensory characteristics of the resultant hydrolysates was investigated. At two degrees of deamidation (24% and 60%, with or without moisture-heating, respectively), wheat gluten pretreated by acetic acid deamidation was more susceptible to be hydrolyzed as evaluated by the hydrolysis degree, nitrogen solubility index, titratable acid amount and free carbohydrate content of the hydrolysates. Wheat gluten pretreated by acetic acid deamidation at a degree of 24% exhibited the highest susceptibility to enzymatic hydrolysis. Moisture-heating (121 °C, 10 min) in the deamidation pretreatment decreased the susceptibility of wheat gluten to enzymatic hydrolysis and the peptide factions of ≤3000 Da in the hydrolysates due to the formation of larger molecule weight aggregates. The hydrolysates prepared from acetic acid deamidated wheat gluten showed more intense glutamate-like and sauce-scented taste and better nutritional characteristics.     

Optimization of formic/acetic acid delignification of Miscanthus × giganteus for enzymatic hydrolysis using response surface methodology

A Box-Behnken experimental design and response surface methodology were employed to optimize the pretreatment parameters of a formic/acetic acid delignification treatment of Miscanthus × giganteus for enzymatic hydrolysis. The effects of three independent variables, namely cooking time (1, 2 and 3 h), formic acid/acetic acid/water ratio (20/60/20, 30/50/20 and 40/40/20) and temperature (80, 90 and 107 °C) on pulp yield, residual Klason lignin content, concentration of degradation products (furfural and hydroxymethylfurfural) in the black liquor, and enzymatic digestibility of the pulps were investigated. The major parameter influencing was the temperature for pulp yield, delignification degree, furfural production and enzymatic digestibility. According to the response surface analysis the optimum conditions predicted for a maximum enzymatic digestibility of the glucan (75.3%) would be obtained using a cooking time of 3 h, at 107 °C and with a formic acid/acetic acid/water ratio of 40/40/20%. Glucan digestibility was highly dependent on the delignification degree.     

Biological pretreatment of sugar cane bagasse for the production of cellulases and xylanases by Penicillium echinulatum

In this study, sugar cane bagasse was pretreated with the white rot fungus Pleurotus sajor-caju PS 2001, and this biomass was subsequently used in the production of cellulases and xylanases by the fungus Penicillium echinulatum. Despite the environmental advantages offered by this type of pretreatment, the enzymatic activity obtained with biologically pretreated sugar cane bagasse (PSCB) was lower than that of the control treatments, which were carried out with untreated sugar cane bagasse (SCB) and cellulose. For medium supplemented with PSCB, the average peak activities obtained were 0.13, 1.0, 0.18, and 0.33 U ml^?1 for FPA, endoglucanase, β-glucosidases, and xylanases, respectively. For the cellulose, control values of 0.52, 1.20, 0.20, and 1.46 U ml^?1, and SCB values of 0.95, 1.60, 0.21, and 1.49 U ml^?1 were obtained, respectively. Although the enzymatic activities of the culture with biologically pretreated sugar cane bagasse were lower than the cultures carried out with untreated sugar cane bagasse, it should be noted that production of enzymes of the cellulase and hemicellulase complex after production of the mushrooms is another way to add value to this agricultural residue.     

Optimization of ethanol production by Saccharomyces cerevisiae UFPEDA 1238 in simultaneous saccharification and fermentation of delignified sugarcane bagasse

Ethanol production by Saccharomyces cerevisiae UFPEDA1238 was performed in simultaneous saccharification and fermentation of delignified sugarcane bagasse. Temperature (32 °C, 37 °C), agitation (80; 100 rpm), enzymatic load (20 FPU/g cellulose and 10%, v/v β-glucosidase or 10 FPU/g cellulose and 5% β-glucosidase) and composition of culture medium were evaluated. Ethanol concentration, enzymatic convertibility of cellulose and volumetric productivity were higher than 25 g/L, 72% and 0.70 g/L h, respectively, after 30 h, when the culture medium 1 and 20 FPU/g cellulose/10%, v/v β-glucosidase or the culture medium 2 and 10 FPU/g cellulose/5% β-glucosidase were used in SSF at 37 °C and 80 rpm. In the SSF with culture medium 2 (supplemented with ammonium, phosphate, potassium and magnesium), 150 L ethanol/t bagasse was achieved, with minimum enzyme loading (10 FPU/g cellulose and 5%, v/v β-glucosidase) for 8%, w/v of solids, which is often an important requirement to provide cost-efficient second generation ethanol processes.     

Sodium carbonate pretreatment: an approach towards desilication of paddy straw and enhancement in biogas production

Lignocellulosic biomass is a useful but an inconvenient form of energy, and paddy straw (PS) is one of the most abundant lignocellulosic wastes on the earth. Lignocellulosics generally have a high content of cellulose having combustion energy of 15 kJ/g which, when converted to methane, have a combustible energy of 50 kJ/g. But lignin and silica are the main deterrents for the microbial action on the cellulose/hemi-cellulose component of PS. In order to break the protective shield made by lignin and silica and to enhance the PS digestibility, the PS was pretreated with different concentrations (2, 4, 6, 8 and 10 %) of sodium carbonate by soaking the PS in sodium carbonate solution for the periods of 24 and 48 h and simultaneously irradiating the other set with microwaves (power 720 W, temperature 180 °C) for 30 and 60 min. The change in chemical composition of PS was the factor determining the enhancement in PS digestibility. Sodium carbonate (4 %) + microwave (60 min) pretreatment was found to be the best amongst the other pretreatments with 84.9 % desilication of PS and 44.3 and 54.4 % increase in cellulose and biogas production, respectively.     

Steam Pretreatment of Rice Hulls to Release Fermentable Saccharides: An Approach to Improve Recovery of (Hemi)Cellulosic Sugars Through Multivariate Design

The conversion of rice hulls into fermentable saccharides was explored through steam pretreatment employing 2.5% SO₂. The interaction between temperature and time was assessed by means of the response surface method to achieve optimum contents of C6-sugars in water-insoluble solids (WIS) and C5-sugars in the liquor. Pretreatment carried out at 218 °C for 2.3 min released liquor containing 55.4 g/L of sugars (29.1 g/L of xylose). In parallel, the WIS was subjected to enzymatic saccharification using different solid and enzyme loads via an experimental design: assays using 22.0% WIS and 20.0 filter paper units (FPU)/g led to 90.6 g/L of glucose, corresponding to a yield of 86.4% and an overall yield of 72.4%. The data reported are the highest ever found for such raw material, making it attractive to compete with conventional lignocellulosic biomass.     

Kinetic modeling of enzymatic saccharification using wheat straw pretreated under autohydrolysis and organosolv process

The enzymatic saccharification kinetics of untreated wheat straw, pretreated solids obtained by a sequence of autohydrolysis (solubilization of hemicellulose) and organosolv (solubilization of lignin) were studied together with two pure cellulose model substrates, filter paper and Avicel. Two kinetic models for glucose production were compared and its kinetic constants calculated. According to the obtained results, enzymatic saccharification of the autohydrolysis pretreated solids (APS) proved to be more effective than when the organosolv pretreated solids (OPS) were used. The maximum extent of the enzymatic conversion of cellulose to glucose was 90.88% and 64.04%, for APS and OPS respectively, at 96 h. This result was probably due to an increase in accessible area for APS and a possible inhibition by phenolic acids deposited on the surface of OPS, acting as a barrier for enzymatic saccharification. Initial saccharification rate for APS and OPS was 0.47 g/(L h) and 0.34 g/(L h), respectively. Models based on first and second order cellulase deactivation kinetics satisfactory predicted the behavior of glucose production, however the second order model had a higher accuracy than the first order one. Visualization of structural modification induced by enzymatic saccharification at 12 h for the pretreated solids was done using scanning electron microscopy.     

Guayule as a feedstock for lignocellulosic biorefineries using ammonia fiber expansion (AFEX) pretreatment

Natural rubber latex extraction from guayule leaves behind greater than 90% (by weight) of agricultural residue as a feedstock suitable for conversion to biofuels via a thermochemical or biochemical route. Untreated guayule shrub and bagasse (after latex extraction) has shown to be very recalcitrant to enzymatic hydrolysis, necessitating application of a chemical pretreatment to enhance cellulase accessibility. The objective of this work was to carry out detailed compositional analysis, ammonia fiber expansion (AFEX¹) pretreatment, enzymatic hydrolysis and ethanol fermentation for various guayule-derived biomass fractions. Plant feedstocks tested were derived from two sources; (a) a mature 2007 AZ-2 whole guayule shrub plant obtained from USDA/ARS² research fields, and (b) the guayule latex-extracted commercial grade bagasse (62505) from Yulex Corporation. Compositional analysis and enzymatic hydrolysis were carried out using standard NREL³ protocols (www.nrel.gov/biomass/analytical_procedures.html). AFEX pretreatment was carried out using concentrated ammonium hydroxide at elevated temperatures for desired residence times in a pressurized reactor. Yeast fermentations on biomass hydrolyzates were carried out micro-aerobically using Saccharomyces cerevisiae (424A strain) in shake flasks.AFEX pretreatment was found to substantially improve overall enzymatic digestibility by 4-20 fold for both untreated guayule shrub and latex-extracted bagasse. Maximum glucan and xylan conversion achieved for the latex-extracted bagasse was 40% and 50%, respectively. The yeast was readily able to ferment both glucose and xylose to ethanol from the guayule bagasse hydrolyzate with or without external nutrient supplementation (i.e., yeast extract and tryptone). Our results highlight the possible utilization of guayule as a feedstock for lignocellulosic refineries co-producing natural rubber latex and biofuels. However, further process improvements (e.g., lignin/resin extraction and cellulose decrystallization using a modified AFEX process) are necessary to increase the effectiveness of ammonia-based pretreatments for further enhancing enzymatic digestibility of guayule-derived hardwood biomass.     

Utilization of pretreated bagasse for the sustainable bioproduction of cellulase by Aspergillus nidulans MTCC344 using response surface methodology

Response surface methodology (RSM) was used to optimize the conditions for the production of endo β-1,4 glucanase, a component of cellulase by Aspergillus nidulans MTCC344 under solid state fermentation, using bagasse as the chief substrate. A four-factor-five-level central composite design was employed for experimental design and analysis of the results. Maximum cellulase activity (CMCase was 28.96 U g⁻¹) can be attained at the optimum conditions, 16.8 mm bagasse bed height, 60% moisture content, pH 4.25 and temperature 40 °C in the solid state fermenter. These data were rather close to the experimental results obtained (CMCase was 28.84 U g⁻¹). A. nidulans MTCC344 was able to hydrolyze pretreated bagasse completely after 8 days of incubation with significant endo β-1,4 glucanase activities. The results of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) of bagasse showed structural changes through pretreatment, in favor of enzymatic hydrolysis. Bagasse with alkali pretreatment using sodium hydroxide is a source of lignocelluloses able to improve the yield of endo β-1,4 glucanase by the strain of A. nidulans. The endo β-1,4 glucanase produced during the bioconversion of cellulose to glucose by A. nidulans MTCC344 is strongly dependent on the pretreatment given before hydrolysis.     

The composition of floury and vitreous endosperm affects starch digestibility kinetics of the whole maize kernel

Maize grain starch is the major energy source in animal nutrition, and its high digestion and utilization largely depend on endosperm traits and the structure of the starch-lipoprotein matrix. The aim of this work was to determine floury and vitreous endosperm traits and its relation to starch digestibility rate. In total, kernels of 30 hybrids were manually dissected, and amylose, total zein and starch and non-starch lipids were determined in both vitreous and floury endosperm. Starch digestibility of the whole kernel was determined based on glucose released during a two-step in vitro pig model of enzymatic digestion, and starch digestibility rate was calculated according to the first-order kinetics. The vitreous endosperm of tested hybrids had higher contents of amylose (204.6 vs 190.4 g/kg), zein (63.2 vs 40.4 k/kg) and starch lipids (5.6 vs 4.9 g/kg), and lower content of non-starch lipids (7.3 vs 9.6 g/kg) than floury endosperm. Digestibility coefficients varied among hybrids, and starch digestibility rate varied from 0.73 to 1.63 1/h. Lipids in both vitreous and floury endosperm negatively correlated with the most of digestion coefficients, whereas zein correlated in vitreous and amylose in the floury endosperm (P < 0.05). Starch digestibility rate negatively correlated with all traits, except amylose content in vitreous endosperm. As a result, a linear regression model with four variables including contents of zein and starch lipids in vitreous and zein and amylose in floury endosperm can predict more than 65% variability of starch digestibility rate of tested hybrids.     

Effects of various water or hydrothermal treatments on certain antinutritional compounds in the seeds of the tribal pulse,Dolichos lablab var.vulgaris L.

Effects of soaking, cooking and autoclaving on changes in polyphenols, phytohaemagglutinating activity, phytic acid, hydrogen cyanide (HCN), oligosaccharides and in vitro protein digestibility were investigated in seeds ofDolichos lablab var.vulgaris. Both distilled water and NaHCO₃ solution soaking and autoclaving significantly reduced the contents of total free phenolics (85–88%) compared to raw seeds. Autoclaving (45 min) reduced the content of tannins by upto 72%. Soaking seemed to have limited effect in eliminating phytohaemagglutinating activity, whereas autoclaving (45 min) seemed to eliminate the haemagglutinating activity completely. The reduction in content of phytic acid was found to be some what greater in distilled water soaking (28%) compared to NaHCO₃ solution soaking (22%). Only a limited loss in content of phytic acid was observed under cooking as well as autoclaving. Loss of HCN was greater under autoclaving (87%) compared to the other processes studied. Of the three sugars analysed, soaking reduced the level of verbascose more than that of stachyose and raffinose. Autoclaving reduced the content of oligosaccharides more efficiently (67–86%) than ordinary cooking (53–76%). Autoclaving improved the in vitro protein digestibility (IVPD) significantly (13%). Of all the different water and hydrothermal treatments studied autoclaving seemed to be the most efficient method in improving IVPD and eliminating the antinutrients investigated except phytic acid.     

Characteristics of destarched corn fiber extrudates for ethanol production

The effect of extrusion on characteristics of destarched corn fiber was investigated. Extrusion was conducted at a screw speed of 300 rpm, feed rate of 100 g/min, feed moisture content of 30%, melt temperature of 140 °C and die diameter of 3 mm. After extrusion, characteristics of raw and extruded destarched corn fiber were compared. Raw and extruded destarched corn fibers were enzymatically saccharified and fermented using Saccharomyces cerevisiae (ATCC 24858). Extrusion pretreatment resulted in low crystallinity index, significant decrease in degree of polymerization and microstructure disruption of destarched corn fiber for enzymatic saccharification. This provides a significant increase in xylose yield for fermentation. Significant increase in protein digestibility and free amino nitrogen were additional benefits of extrusion for yeast nutrient in fermentation. Therefore, extruded destarched corn fiber significantly increased (p < 0.05) ethanol yield (29.08 g/L) and higher conversion (88.79%) by improving the physiochemical and functional properties for saccharification and fermentation.     

Influence of phytate on in vitro digestibility of casein under physiological conditions

The phytic acid content of four different varieties of beans under different processing conditions was estimated. It was highest in red kidney (1.86–2.13%) slightly lower in pigeon (1.86–2.03%), white (1.80–1.96%) and black eyed beans (1.15–1.64%). There was no significant change in phytic acid content of beans after soaking at 25°C for 22 hours. However, both soaking and cooking revealed 26–37% loss of phytic acid in all four varieties of beans.The rate of in vitro casein digestibility with and without phytic acid at concentrations found in legumes was determined at pH 8 and 37°C using multienzyme technique. Addition of 5 mg Na-phytate reduced the casein digestibility up to 20% compared to the control. However, only 25% reduction of casein digestibility was observed in the presence of 25 mg of Na-phytate. Higher concentration of Na-phytate had no significant effect on the rate of casein digestibility. Data strongly suggest the formation of protein phytate complex at alkaline pH of small intestine.Part of this work was presented at the XIII International Congress of Nutrition in Brighton, UK in August 1985.     

Effect of partial gelatinization and retrogradation on the enzymatic digestion of waxy rice starch

The effect of partial gelatinization and retrogradation on in vitro enzymatic digestibility of waxy rice starch was investigated, and the relationship between the residual crystallinity and digestibility measured. An aqueous dispersion of starch (5%, dry weight basis) was partially gelatinized by heating at different temperatures (60, 65, or 70 °C for 5 min). The relative melting enthalpy values of the starch samples, based on the melting enthalpy of native starch, were 69.0, 36.7, and 8.5%, respectively. Retrograded starch samples were also prepared by storing a fully gelatinized starch paste (5% starch) at 4 °C for 2, 4, or 7 d, and the relative melting enthalpy values for the starch samples were 36.7, 67.2, and 79.9%, respectively. The partial gelatinization and retrogradation changed the enzymatic digestion behavior of the waxy rice starch samples, and the changes were significant in the initial stage of digestion. The digestion rate was reduced as the melting enthalpy increased. The amounts of slowly digestible starch (SDS) and resistant starch (RS) correlated positively with the relative melting enthalpy of the partially gelatinized or retrograded starch samples. The glycemic index (GI) estimated using an in vitro digestion test correlated negatively with the relative melting enthalpy. At similar melting enthalpy levels, the partially gelatinized starch samples were more resistant to enzymatic digestion than the retrograded starch samples, indicating that the thermal history and the crystalline morphology affected the enzymatic digestion behavior of starch.     

辣木的染色体制片优化及核型分析

以辣木分生组织为材料,采用酶解去壁低渗法制片,探讨不同取材部位、预处理方式和酶解时间对辣木染色体制片的影响,并对其进行核型分析,以期为辣木的起源、演化及遗传育种提供一定理论依据。结果表明:以辣木新枝茎尖为最佳取材部位,用饱和对二氯苯预处理2 h,再用4%纤维素酶和5%果胶酶混合物酶解4 h,制片所得染色体效果最佳。核型分析表明,辣木染色体属于小染色体,有28条,核型公式为2n=2x=2n=28m,属于1B类型,核型不对称系数60.29%,核型对称程度较高,这表明辣木在进化中可能处于比较原始类型。     

Optimization of the solid state fermentation process to obtain tempeh from hardened chickpeas (Cicer arietinum L.)

Solid state fermentation (SSF) represents a technological alternative for a great variety of cereals and legumes, orcombination of them, to improve their nutritional quality and to obtain edible products with palatable sensorial characteristics. The objective of this work was to find the best conditions of fermentation temperature and time to obtain tempeh from hardened chickpeas (Cicer arietinum L.) applying SSF. Response surface methodology(RSM) was applied over three response variables (phytic acid, in vitro protein digestibility and available lysine) to find best conditions of fermentation to carry out the process. A central composite experimental design with two factors [X₁ = temperature (31–36 ^°C) and X₂ = time (48–72 h)] in five levels (2 factorials,2 axial, I central) was used. Spores from Rhizopus stolonifer were suspended in distilled water (1 ×10⁶ spores/mL) and used as starter. According to regression models, minimum and maximum levels of the response variables were 1.24–2.66 mg phytic acid/g ofsample DM, 77.6–83.5% in vitro protein digestibility and2.18–4.63 g available lysine/16 g N. The superposition ofcontour plots of each one of the response variables allowedresearchers to find, graphically, the best conditions for the SSF process: 35.8 ^°C for 42.7 h.     

Optimization for enzyme-retting of flax with pectate lyase

Flax (Linum usitatissimum L.) is an important commercial crop that supplies both linseed and bast fibers for multiple applications. Retting, which is a microbial process, separates industrially useful bast fibers from non-fiber stem tissues. While several methods (i.e., water- and dew-retting) are used to ret flax, more recently enzymes have been evaluated to replace methods used currently. Alkaline pectate lyase (PL) from the commercial product BioPrep 3000 and ethylenediaminetetraacetic acid (EDTA) from Mayoquest 200 as a calcium chelator were used in various formulations to ret flax stems. Retted stems were then mechanically cleaned through the USDA Flax Fiber Pilot Plant and passed through the Shirley Analyzer. The PL and chelator effectively retted flax from both fiber flax and linseed stems, and the use of enzyme plus chelator retted flax stems better than either component alone. Fiber yield and strength were greater than retting with a mixed-enzyme product that contained cellulases. Retting with PL and chelator was optimized based on fine-fiber yield, remaining shive content, and fiber properties. PL at levels of about 2% of the commercial product for 1 h at 55 °C followed by treatment with 18 mM EDTA for 23–24 h at 55 °C provided the best fibers based on these criteria. Yield and fiber properties determined by these tests were not improved with PL levels of 5% of the commercial product.     

Inclusion of alfalfa improves nutritive value and in vitro digestibility of various straw–grass mixed silages in Tibet

To enlarge the feed resources and enhance the utilization efficiency of straws as ruminant feed in Tibet, four kinds of local crop straws with tall fescue (Festuca arundinacea Schreb.) based on the ratio of 40/60 (fresh weight) were ensiled with four levels (0, 10%, 20% and 30% of fresh weight) of alfalfa (Medicago sativa L.), respectively. The laboratory silos (1L) were opened after 45 days of ensiling, and the fermentation characteristics, nutritive value and in vitro digestibility of the mixed silages were analysed. The silages including alfalfa had significantly (p < 0.05) or numerically (p > 0.05) higher lactic acid and crude protein contents, lactic acid bacteria counts, in vitro digestibility of dry matter, neutral detergent fibre (NDF) and acid detergent fibre (ADF), and lower NDF and ADF contents than controls. The results suggest that inclusion of alfalfa to mixtures of straws and tall fescue had favourable effects on fermentation quality and obviously improved the nutritive value and in vitro digestibility of mixed silages. This effect was most evident when the inclusion proportion of alfalfa was 30% in oat straw mixed silage.