Combined chemical and enzymic treatments of corn husk lignocellulosics

The potential for using corn (Zea mays L) husk residues (carbohydrates 827 g kg^?1, lignin 66 g kg^?1 DM) as a carbohydrate source for the production of soluble sugars by combined chemical pretreatment and enzymic hydrolysis was assessed. Comparative investigations of acidic and alkaline pretreatments on corn husk have shown that pentose-containing carbohydrates comprised 86–93% of the solubilised fraction. While pretreatments with 1.25 M NaOH at 25.85° C resulted in preferential extraction of hemicellulose having DP; > 12, acid pretreatments 0.51 M H₂SO₄, 0.51 M H₃PO₄ at (85° C) resulted in extensive depolymerisation of this polysaccharide. Xylose and low molecular weight carbohydrates were identified as the major products. Subsequent hydrolysis of the solubilised fraction with crude hemicellulase preparations yielded 40.90% fermentable sugars. When NaOH (0.02–1.25 M), H₂SO₄ and H₃PO₄ (0.02–0.51 M) were used as pretreatment solvents (25–85° C, 2 h), NaOH was the most effective in increasing the susceptibility of the residual husk towards enzymes, yielding 83–96% reducing sugars. This solvent solubilised up to 60.6% of the lignin and appeared to disintegrate the fibrillar structure of husk. The crystallinity of husk residues increased following the chemical pretreatments and was positively correlated with cellulose content. Enzymic hydrolysis with commercial cellulase preparations proceeded in two stages: a rapid breakdown of amorphous cellulose after which the hydrolysis rate levelled off. Similar biphasic patterns were observed for the pyrolysis temperature of cellulose. Under the most optimal conditions for husk saccharification (pretreatment with 1.25 M NaOH, 25° C, 2 h, followed by enzymic hydrolysis using a mixture of cellulase and cellobiase), 96% of the cellulose-enriched residues was hydrolysed to reducing sugars. A cellulase preparation from Trichoderma reesei exhibited substantial hemicellulolytic activity and could, therefore, be used as the sole saccharifying enzyme preparation for husk lignocellulosics.     

Influence of Ethanolic Soaking of Soybeans on Flavor and Lipoxygenase Activity of Soymilk

Soymilks were prepared from soybeans soaked in 15% ethanol and in 15% ethanol plus 0.1M NaOH, 0.1M Na₂CO₃ or 0.1M NaHCO₃ for various times at 60°C. The ethanol was removed before processing the soybeans into soymilks, and the soymilks were analyzed for composition, lipoxygenase activity, TBA number, and flavor (paintiness, grassiness, nuttiness, cereal, and astringency). The change in paintiness with time of soaking did not depend only on lipoxygenase activity or on TBA number, but was related to the soaking conditions. Soaking in 0.1M NaOH gave soymilks with more paintiness than soaking in either 0.1M Na₂CO₃ or NaHCO₃.     

Biodegradation of cell wall components of maize stover colonized by white-rot fungi and resulting impact on in-vitro digestibility

Treatment of crop residues with some species of white-rot fungi can enhance digestibility. This study was conducted to investigate changes in in-vitro dry matter disappearance (IVDMD) and degradation of cell wall constituents in maize (Zea maize L) stover treated with three white-rot fungi: Cyathus stercoreus, Phlebia brevispora and Phanerochaete chrysosporium. Solid fermentation of maize stover for 28 days at 27°C improved IVDMD from 409 g kg^?1 (control) to 514 g kg^?1 for P brevispora and 523 g kg^?1 for C stercoreus. In contrast, growth of P chrysosporium reduced IVDMD from 409 to 298 g kg^?1. All fungi degraded cell wall p-coumaric acid (PCA) and ferulic acid (FA), but P chrysosporium was the least effective in degrading PCA and FA. Conversely, P chrysosporium degraded lignin 1·6 times more effectively than C stercoreus and 1·4 times more than P brevispora, indicating that lignin degradation alone cannot account for the IVDMD enhancement and that degradation of PCA and FA may be important. Hemicelluloses were preferentially and highly utilized by all the fungi. Cellulose was extensively degraded only by P chrysosporium (69% lost after 28 days of incubation), while substrate colonized by the other two fungi retained more than 84% original cellulose. Incubation of C stercoreus and P brevispora decreased the concentrations of both xylose and arabinose, but increased glucose concentration, whereas P chrysosporium removed less xylose and decreased glucose concentration. Preferential removal of arabinose over xylose by the fungi caused an increase in the xylose to arabinose ratio of the treated residues. Enhanced digestibility may have resulted from cleavage of lignin-carbohydrate bonds. Results of this study suggest that digestibility enhancement of maize stover colonized by white-rot fungi is regulated by a complex combination of various factors, including the degradation of structural carbohydrates, cell wall phenolic acids and lignin.     

Relationship among compositional data of fibrous by-products as determined by two different extractions in the detergent system of analysis. Influence on the prediction of the digestibility

Both direct and sequential extractions in the detergent system of analysis were applied to some fibrous by-products (cereal and legume straws, legume bagasse, vine branch silage and poplar bark) to determine which gave the better prediction of the digestibility through the summative equation, and to study the interferences of fibre-bound nitrogen and tannins. Permanganate lignin gave a lower correlation than acid-detergent lignin when figures from direct and sequential extractions were compared. Fibrebound nitrogen (as N × 6.25) was positively correlated to permanganate lignin, whereas tannins were positively correlated to acid-detergent lignin. Figures for permanganate lignin from sequential extraction and aciddetergent lignin from direct extraction gave a good prediction of in-vitro digestibility when they were used in the summative equation. More research into lignin, tannins and the detergent system of analysis of fibrous by-products should be done in order to improve and clarify the prediction of digestibility.     

Base-Mediated Firmness Retention of Sweetpotato Products

Sweetpotato strips vacuum-infiltrated with 0.01–0.15M solutions of Na₃PO₄, Na₂CO₃, NH₄OH, or NaOH prior to heat processing were firmer than untreated, heat-processed strips. Among the bases Na₃PO₄ and Na₂CO₃ were most effective. When base-treated, cooked tissue was adjusted to its normal pH range (5.9–6.2) and reheated, the retention of firmness did not decrease. Using calcium chloride solution in conjunction with base treatment further increased firmness retention. This process was applied on strips but could readily be adapted to other types of sweetpotato products ranging from dice to chunks.     

Utilisation of Egyptian rice straw in production of cellulases and microbial protein: Effect of various pretreatments on yields of protein and enzyme activity

Rice straw was chosen as a cheap carbon source for SCP production using a locally isolated fungus identified as Trichoderma harzianum. The chemical constituents of the raw material were cellulose 43%, hemicellulose 26% and relatively low lignin, 16%. The effects of chemical and physical pretreatments on the protein production, cellulase activity and cell mass of T. harzianum have been investigated. Pretreatment of the raw material using a combination of NaOH and high pressure steam treatment increased its microbial digestibility from 24% to 73%. Similar results were obtained by pretreatment with sodium chlorite for holocellulose formation. However, maximum yields of cell mass and protein were obtained by the first method. The organism gave 7.18 g litre^?1 cell mass and 2.50 g litre^?1 mycelial protein. Treatment with sodium chlorite increased cellulase activities but gave a lower fungal yield. When the NaOH was applied with high pressure steam, the organism produced 32.8% crude protein, a yield similar to that given by the same organism cultured on soluble carboxymethylcellulose.     

Effect of Magadi soda treatment on the tannin content and in-vitro nutritive value of grain sorghums

Studies were conducted to investigate the possible use of raw Magadi soda (RMS), a sodium sesquicarbonate salt (Na₂CO₃NaHCO₃. H₂O) in the detoxification of the tannins associated with high- and low-tannin sorghum grains and to establish the relative in-vitro nutritive value of the treated grains. Treatment of grains with concentrations as low as 4 g litre^?1 of RMS for 3 days, reduced the level of the assayable tannins in the grains by 40 to 57%. This reduction was accompanied with an increase in the in-vitro digestibility of the organic matter and starch. Treatment of the hightannin sorghums increased the in-vitro protein digestibility while no increase was observed for the low-tannin sorghums. Use of solutions containing more than 37.5 and 9 g RMS litre ^?1, resulted in reduced protein digestibility of the high- and lowtannin containing sorghums, respectively.     

Effect of delignification on the in vitro rumen digestion of polysaccharides of bagasse

Sugar cane bagasse was partially delignified by three different chemical methods, viz. sodium sulphide/hydroxide (Kraft process), sodium hydroxide and sodium sulphite. The Kraft and alkali treatments each reduced the lignin content by about 55%, and increased the rumen dry matter digestibility (d.m.d., measured by an in vitro method) by over 170%. Treatment of the bagasse with sodium sulphite removed only 15% of the lignin and increased the d.m.d. by only 37%. The digestibility of hemicelluloses (measured as xylan and arabinan) and cellulose in delignified bagasse increased fourfold and twofold, respectively, for the Kraft and alkali treatments and twofold for the sodium sulphite treatment.     

Nutrient digestibility response to graded dietary levels of sodium chloride in weanling pigs

BACKGROUND: Sodium (Na⁺), chloride (Cl^?) and phosphorus (P_i) are involved in a number of metabolic and physiological processes in the body, and these mineral elements must be supplied to the animal via the diet. The intention of this study was to evaluate the effect of dietary supplementation with different levels of sodium chloride (0.1, 0.2, 0.3, 0.4, 0.5 and 0.6% NaCl) on apparent and true P digestibility (APD and TPD) and dry matter (DM), crude protein (CP) and calcium (Ca) digestibility in weanling pigs. RESULTS: Dietary NaCl had a quadratic effect on both APD and TPD (P < 0.05) but not on DM, CP and Ca digestibility (P > 0.05). At an NaCl concentration of 0.41% the APD and TPD values were 41.5 and 53.3% respectively. CONCLUSION: These results suggest that a high level of dietary Na⁺ may enhance P absorption and improve its digestibility by coupling Na⁺ transportation to P_i absorption via the energy‐requiring Na⁺/P_i co‐transporter. Copyright © 2008 Society of Chemical Industry     

Responses of Lotus corniculatus to environmental change. 2. Effect of elevated CO2, temperature and drought on tissue digestion in relation to condensed tannin and carbohydrate accumulation

Clonal plants of three genotypes of Lotus corniculatus (cv Leo) were grown in eight controlled environments under combinations of two temperature regimes, two CO₂ concentrations and two watering regimes. Condensed tannins (proanthocyanidins), in-vitro digestibility, initial rates of gas evolution (as an indicator of the initial rates of fermentation of the substrate), volatile fatty acid evolution, and non-structural carbohydrate (NSC) levels were determined in leaves, stems and roots at full flowering. Under control conditions (average midsummer conditions in the United Kingdom) the total condensed tannin content of leaves varied six-fold between genotypes but condensed tannin contents in stems and roots were similar. Condensed tannin levels were significantly increased in leaves and stems of all three genotypes by doubling the CO₂ concentration while raising the temperature towards the optimum for growth significantly reduced condensed tannin levels. Drought stress significantly reduced condensed tannin levels in leaves and, particularly, in roots. Nutritive value was inversely related to condensed tannin levels in leaves and a negative relationship was observed between condensed tannin concentrations of more than 25–30 g kg⁻¹ dry matter and the initial rates of gas evolution when subjected to in-vitro fermentation with rumen micro-organisms. In leaves, digestibility was significantly increased by drought and by increasing temperature but reduced by high CO₂. In stems, digestibility was significantly increased by drought, but not significantly affected by increasing temperature, or by high CO₂ alone. In roots, digestibility was significantly increased by drought, and decreased by increasing temperature or CO₂. Increasing the growth temperature towards optimum growth reduced the content of NSC in all tissues with the greatest changes occurring in root tissue. Doubling the CO₂ concentration increased NSC levels in leaves and stems with starch content more than doubled under high CO₂ while, in roots, increased levels were only observed in combination with drought stress. There was a linear correlation between condensed tannin concentration and total NSC that was positive for leaves, neutral for stems and negative for roots. The relationship between carbohydrate levels and rates of gas production was negative for leaves and positive for stem and roots. © 1999 Society of Chemical Industry     

Isolation of Gellan Gum from Foods by Use of Monovalent Cations

Gellan gum added to foods was recovered by precipitation with 2M NaCl. The precipitate was trapped on glass wool, washed with 1M salt solution and eluted with boiling 40% H₂SO₄ or boiling 2 × 10^?4N NaOH. Elution with dilute NaOH was as effective as use of 40% H₂SO₄, except with dog food, mayonnaise and salad dressing. The hydrocolloid content of the eluate was determined by the carbazole test. Recoveries from milk, beverages, salad dressing and other foods ranged from 75–94% (reproducibility 2–4%). The preferred cations for precipitation were Na⁺ > K⁺ > Li⁺ > NH₄⁺. For the anions, the order was CO₃^? > SO₄^? > Cl^?.     

杨木APMP制浆化学预处理废液中有机物的分析

研究了不同化学预处理条件对APMP废液中木素和糖类物质浓度的影响。结果表明,化学预处理过程中化学药剂NaOH用量、H₂O₂用量和Na₂SiO₃用量对化学预处理废液中木素和糖类物质浓度的变化有不同影响,影响程度由大到小依次为NaOH用量＞H₂O₂用量＞Na₂SiO₃用量,其中NaOH用量和H₂O2用量对木素和糖类物质浓度的变化有重要影响,Na₂SiO₃用量无明显影响。化学预处理温度对化学预处理废液中木素和糖类物质浓度的影响程度明显大于化学预处理时间。在化学预处理过程中,NaOH用量、H₂O₂用量和化学预处理温度是影响杨木APMP制浆化学预处理废液中木素和糖类物质浓度的重要因素。     

Influence of Chemical Pretreatment on the Dissolved Organics in Poplar Alkaline Peroxide Mechanical Pulping Effluent

The components of the effluent from the chemical pretreatment of poplar alkaline peroxide mechanical pulp (APMP) were analyzed in this study. The main dissolved organics were low-molecular weight (LMW) lignin, oligosaccharides, and monosaccharides. The lignin and sugar concentrations in the effluent obtained using different chemical pretreatment conditions and chemical dosages were analyzed using ultraviolet (UV) spectroscopy. This analysis provided a theoretical basis for the subsequent treatment and utilization of APMP effluent. The experimental results showed that the dosages of NaOH, H₂O₂, and Na₂SiO₃ in the chemical pretreatment process affected the lignin and sugar concentrations in the effluent and that different chemicals had differing degrees of influence. The degree of influence exhibited the following order: NaOH>H₂O₂>Na₂SiO₃. More specifically, the dosages of NaOH and H₂O₂ had stronger influences on the lignin and sugar concentrations than that of Na₂SiO₃. Indeed, the Na₂SiO₃ dosage hardly affected the lignin and sugar concentrations in the effluent, but Na₂SiO₃ could stabilize the chemical pretreatment system and improve the reactive efficiency of NaOH and H₂O₂. The pretreatment temperature and time also affected the organic components, and the influence of the temperature was stronger than that of time.     

Biodegradation of plant cell walls,wall carbohydrates,and wall aromatics in wheat grown in ambient or enriched CO2 concentrations

Mature internodes from wheat (Triticum aestivum L) grown in control (ambient at c 370 μnol mol^?1) or enriched (to 550 μmol mol^?1) concentrations of atmospheric CO₂ in the free-air CO₂ enrichment (FACE) system were analyzed for potential changes in biodegradation of constituents due to predicted increases in atmospheric levels of CO₂. The first internodes below the grain were incubated with the lignocellulose-degrading white rot fungus, Phanerochaete chrysosporium K-3, or incubated without microorganisms. Plant samples were then analyzed for dry weight loss, disposition of specific cell types to biodegradation using electron microscopy, carbohydrates and lignin using solid state NMR spectroscopy, and ester-and ether-linked aromatics using gas chromatography. Phanerochaete chrysosporium extensively degraded stems cells (c 75%) and both carbohydrate and aromatic portions of the wheat stems; proportionately more carbohydrates were removed by the fungus from the stems. Enriched CO₂ did not affect the chemical composition of wheat stems or the biodegradation by P chrysosporium of plant cell walls or wall components for the most part. Data from various methods all indicated that enriched CO₂ did not substantially alter the biodegradation of wheat cell wall internodes or wall components. Evidence was not found for an influence on C cycling due to CO₂ concentrations in this study.     

Effects of Alkaline and Acid Pretreatments on Alaska Pollock Skin Gelatin Extraction

Pretreatments with different alkalis and acids at different concentrations were used to determine their effects on gelatin extraction from Alaska pollock skin. The alkaline pretreatments with the OH concentrations lower than 0.5 mol/L removed noncollagenous proteins without significant loss of skin collagen. The acid pretreatments caused loss of collagen, even using a weak acid with a low H concentration at a low temperature. The presence of proteases might cause degradation of gelatin extract, but the pretreatments with NaOH or Ca(OH)₂ at 0.1 mol/L OH concentration, or acetic acid at 0.05 mol/L H concentration could significantly decrease the degradation by proteases. The combination of an alkaline pretreatment followed by an acid pretreatment not only removed the noncollagenous proteins, but also provided the proper pH condition for extraction, during which some cross‐linkages could be further destroyed but with less breakage of polypeptide chains.     

Lignin Impact on Fibre Degradation: 1—Quinone Methide Intermediates Formedfrom Lignin DuringIn VitroFermentation ofCorn Stover*

Experiments were conducted to determine whether formation of quinone methide intermediates from lignin occurs during ruminal fermentation of corn stover, as indicated by nucleophilic addition reaction with sulphur-containing reducing agents. Corn stover leaf and stem fractions harvested at full maturity were incubated in buffered ruminal fluid without reducing agents or with (NH₄)₂SO₄ (S-control), Na₂S.9H₂O, cysteine-HCl (cysHCl), or cysHCl plus Na₂S.9H₂O; and in only buffer with or without cysHCl plus Na₂S.9H₂O. Mixed reducing agents (cysHCl plus Na₂S.9H₂O) enhanced ( P< 0.001) in vitro fibre degradation after 48 h, tended to increase solubilisation of fibre ( P =0.07) and dry matter ( P =0.06) in buffer alone, and elevated ( P< 0.001) S-content of residual fibre. In vitro incorporation of S into the undegraded fibre was determined for corn stover fractions of varying lignin compositions that were harvested at two maturities (early dent and full maturity) in 2 years. Extent of fibre degradation was correlated with extent of S-incorporation ( r =-0.54, P< 0.001), and with lignin methoxyl content ( r =-0.84, P< 0.001). The negative association of lignin methoxyl content with digestibility is explained by the relative likelihood of quinone methide intermediate formation from guaiacyl and syringyl units in lignin.     

Integral utilisation of barley husk for the production of food additives

A new and effective chemical–biotechnological process for the global utilisation of barley husk (obtained from the spent grains in the brewing process) is reported. With the proposed process the three main components of the lignocellulosic residue (cellulose, hemicellulose and lignin) are utilised. A first treatment with sulfuric acid (pre‐hydrolysis) allowed the solubilisation of hemicelluloses to give xylose and glucose‐containing liquors (suitable to make fermentation media for the continuous lactic acid (LA) production with L. pentosus) and a solid phase containing cellulose and lignin. In this set of experiments, a maximum volumetric productivity (Q_P) = 2.077 g L^?1 h^?1 and product yield (Y_P/S) = 0.62 g g^?1 were obtained for a dilution rate of 0.01 h^?1. The solid residues from pre‐hydrolysis were treated with NaOH in order to increase their cellulase digestibility, and dissolve the lignin content. The cellulose residue was used as substrates for lactic acid production by simultaneous saccharification and fermentation (SSF) in media containing Trichoderma reesei cellulases and Lactobacillus rhamnosus cells using the complete MRS broth or a cheaper medium. In both cases similar LA concentrations and volumetric productivities were achieved (P = 73.4–71.0 g L^?1 and Q_P = 1.28–1.25 g L^?1 h^?1, respectively), where P is LA concentration. The lignin solution obtained after the alkaline treatment was extracted with ethyl acetate in order to obtain the phenolic components. The extract obtained at pH 3 showed three times more antioxidant activity than the one extracted at pH 12.8, with an EC₅₀ of 1.396 g L^?1 for pH 3 and 4.604 g L^?1 for pH 12.8. The best extracts showed twice antioxidant activity than BHT. Copyright © 2007 Society of Chemical Industry     

Optimization of Processing Parameters for the Preparation of Flounder Frame Protein Product

Flounder frame was used as a raw material for the preparation of protein product. Processing parameters were evaluated using both fresh and frozen ground frames. The results indicate the following optima: (1) pH of extraction medium, ii; (2) extraction time, 60 min; (3) volume to weight ratio, 10: 1; (4) extraction temperature, 23°C. Isoelectric precipitation was conducted at pH 5 using KCI or H₃PO₄. Results indicate that NaOH was more effective than Ca(OH)₂ in solubilizing frame protein at pH 11. Ground frozen flounder frames gave a 10% decrease in protein extractability when compared to fresh frames using NaOH as the extractant and a 22% decrease when Ca(OH)₂ was employed as the extractant. Approximately 70% of the protein is recovered using the NaOH-HCI system.     

Pasting properties of Angelica dahurica starches in the presence of NaCl,Na2CO3, NaOH,glucose, fructose and sucrose

The pasting viscosities of starches from Angelica dahurica (three cultivars named Chuan Baizhi, Yu Baizhi and Qi Baizhi in Chinese, respectively), in the presence of NaCl, Na₂CO₃, NaOH, glucose, fructose and sucrose were determined with a rapid visco analyser. The pasting peak, trough or final viscosities and the pasting temperatures (Pt) of Baizhi starches increased with NaCl concentration increased from 0 to 3.0%. The peak viscosities of Baizhi starches increased at 0.2% Na₂CO₃ concentration and then decreased with Na₂CO₃ concentration up to 0.8%. The trough and final viscosities and the Pt decreased with Na₂CO₃ concentration up to 0.8%. The peak viscosities increased in 0.1%, but decreased in 0.2% NaOH concentration. The trough and final viscosities and the Pt decreased in the presence of NaOH. With the concentration of sugar (glucose, fructose and sucrose) increased from 0 to 20%, the pasting peak, trough and final viscosities of these starches increased significantly. For the same Baizhi starch, the elevation of peak viscosity was the most significant when fructose was added, and the elevation of final viscosity was the greatest when sucrose was added.     

Evaluation of Two Sets of Sorghum Bagasse Samples as the Feedstock for Fermentable Sugar Recovery via the Calcium Capturing by Carbonation (CaCCO) Process

Abstract: Sorghum bagasse samples from two sets (n6 and bmr6; n18 and bmr18) of wild-type and corresponding “brown midrib” (bmr) mutant strains of sweet sorghum were evaluated as the feedstock for fermentable sugar recovery via the calcium capturing by carbonation (CaCCO) process, which involves Ca(OH)₂ pretreatment of bagasse with subsequent neutralization with CO₂ for enzymatic saccharification. Saccharification tests under various pretreatment conditions of the CaCCO process at different Ca(OH)₂ concentrations, temperatures or residence periods indicated that bmr strains are more sensitive to the pretreatment than their counterparts are. It is expected that variant bmr6 is more suitable for glucose recovery than its wild-type counterpart because of the higher glucan content and better glucose recovery with less severe pretreatment. Meanwhile, bmr18showed higher scores of glucose recovery than its counterpart did, only at low pretreatment severity, and did not yield higher sugar recovery under the more severe conditions. The trend was similar to that of xylose recovery data from the two bmr strains. The advantages of bmr strains were also proven by means of simultaneous saccharification and fermentation of CaCCO-pretreated bagasse samples by pentose-fermenting yeast strain Candida shehatae Cs 4R. The amounts needed for production of 1 L of ethanol from n6, bmr6, n18, and bmr18samples were estimated as 4.11, 3.46, 4.03, and 3.95 kg, respectively. The bmr strains seem to have excellent compatibility with the CaCCO process for ethanol production, and it is expected that integrated research from the feedstock to bioprocess may result in breakthroughs for commercialization.