纸浆废料生物炼制细菌纤维素的研究

细菌纤维素(bacterial cellulose,BC)是一种由微生物产生的具有纳米结构的纤维素材料。BC生产的培养基成本偏高,限制了其规模化工业生产和商业应用。为开发新的BC生产原料,通过Cellic CTec 2纤维素酶直接水解硫酸盐和亚硫酸盐两种纸浆废料获得可发酵糖,以其成功制备出BC并研究比较了两种酶解液对BC产量和结构的差异。结果表明,硫酸盐纸浆废料获得的BC产量最高,达9.0 g/L,比亚硫酸盐纸浆废料的7.7 g/L高了17%。两种原料制备的BC膜的结晶度分别为61%和66%,比葡萄糖制备的(78%)低。红外光谱分析表明,不同碳源制备的BC膜的成分没有明显差异。     

Biogas production from anaerobic co-digestion of waste activated sludge: co-substrates and influencing parameters

Reviews in Environmental Science and Bio/Technology - Anaerobic digestion is a versatile biotechnology to treat waste activated sludge (WAS), the main by-products of biological wastewater...     

Effect of azithromycin on enhancement of methane production from waste activated sludge

In the methane production from waste activated sludge (WAS), complex bacterial interactions in WAS have been known as a major contribution to methane production. Therefore, the influence of bacterial community changes toward methane production from WAS was investigated by an application of antibiotics as a simple means for it. In this study, azithromycin (Azm) as an antibiotic was mainly used to observe the effect on microbial changes that influence methane production from WAS. The results showed that at the end of fermentation, Azm enhanced methane production about twofold compared to control. Azm fostered the growth of acid-producing bacterial communities, which synthesized more precursors for methane formation. DGGE result showed that the hydrolysis as well as acetogenesis stage was improved by the dominant of B1, B2 and B3 strains, which are Clostridium species. In the presence of Azm, the total population of archaeal group was increased, resulting in higher methane productivity achievement.     

Production of cellulosic ethanol and enzyme from waste fiber sludge using SSF,recycling of hydrolytic enzymes and yeast,and recombinant cellulase-producing Aspergillus niger

Bioethanol and enzymes were produced from fiber sludges through sequential microbial cultivations. After a first simultaneous saccharification and fermentation (SSF) with yeast, the bioethanol concentrations of sulfate and sulfite fiber sludges were 45.6 and 64.7 g/L, respectively. The second SSF, which included fresh fiber sludges and recycled yeast and enzymes from the first SSF, resulted in ethanol concentrations of 38.3 g/L for sulfate fiber sludge and 24.4 g/L for sulfite fiber sludge. Aspergillus niger carrying the endoglucanase-encoding Cel7B gene of Trichoderma reesei was grown in the spent fiber sludge hydrolysates. The cellulase activities obtained with spent hydrolysates of sulfate and sulfite fiber sludges were 2,700 and 2,900 nkat/mL, respectively. The high cellulase activities produced by using stillage and the significant ethanol concentrations produced in the second SSF suggest that onsite enzyme production and recycling of enzyme are realistic concepts that warrant further attention.     

Continuous ethanol production from concentrated wood hydrolysates in an internal membrane-filtration bioreactor

Continuous culture for the production of ethanol from wood hydrolysate was carried out in an internal membrane-filtration bioreactor. The hydrolysate medium was sterilized at a relatively low temperature of 60 degrees C with the intention of reducing the formation of inhibitory compounds during the sterilization. The maximum ethanol concentration and productivity obtained in this study were 76.9 g/L and 16.9 g/L-h, respectively, which were much higher than those (57.2-67 g/L and 0.3-1.0 g/L-h) obtained in batch cultures using hydrolysate media sterilized at 60 degrees C. The productivity was also found to be much higher than that (6.7 g/L-h) obtained in a continuous cell retention culture using a wood hydrolysate sterilized at 121 degrees C. These results show that the internal membrane-filtration bioreactor in combination with low-temperature sterilization could be very effective for ethanol production from wood hydrolysate.     

Continuous ethanol production from pineapple cannery waste using immobilized yeast cells

The cells of Saccharomyces cerevisiae ATCC 24553, were immobilized in k-carrageenan and packed in a tapered glass column reactor for ethanol production from pineapple cannery waste at temperature 30 degrees C and pH 4.5. The maximum productivity was 42.8 g ethanol 1(-1) h(-1) at a dilution rate of 1.5 h(-1). The volumetric ethanol productivity of the immobilized cells was ca. 11.5 times higher than the free cells. The immobilized cell reactor was operated over a period of 87 days at a dilution rate of 1.0 h(-1), without any loss in the immobilized cell activity. The maximum specific ethanol productivity and specific sugar uptake rate of the immobilized cells were 1.2 g ethanol g(-1) dry wt. cell h(-1) and 2.6 g sugar g(-1) dry wt. cell h(-1), respectively, at a dilution rate of 1.5 h(-1).     

Anaerobic digestion of wood ethanol stillage using upflow anaerobic sludge blanket reactor

The anaerobic digestion of wood ethanol stillage in a UASB reactor was studied. At organic loading rates be low 16 kg COD/m(3) day the reactor performed effectively, achieving soluble COD and BOD removals in excess of 86 and 93%, respectively. Removal of color averaged 40%. At a loading rate of 16 kg COD/m(3) day the methane yield was 0.302 L CH(4) (STP)/g COD removed, and the observed cell yield was 0.112 g VSS/g COD removed. Operation of the reactor at higher loading rates was unsuccessful. Nitrogen, phosphorus, and alkalinity were supplemented. No additions of the essential trace elements Fe, Co, and Ni were required.     

Potential of agroindustrial waste from olive oil industry for fuel ethanol production

Olive pulp (OP) is a highly polluting semi-solid residue generated from the two-stage extraction processing of olives and is a major environmental issue in Southern Europe, where 80% of the world olive oil is produced. At present, OP is either discarded to the environment or combusted with low calorific value. In this work, utilization of OP as a potential substrate for production of bioethanol was studied. Enzymatic hydrolysis and subsequent glucose fermentation by baker's yeast were evaluated for OP from 10% to 30% dry matter (i.e., undiluted). Enzymatic hydrolysis resulted in an increase in glucose concentration by 75%, giving final glucose yields near 70%. Fermentation of undiluted OP hydrolysate (OPH) resulted in the maximum ethanol produced (11.2 g/L) with productivity of 2.1 g/L/h. Ethanol yields were similar for all tested OPH concentrations and were in the range of 0.49-0.51 g/g. Results showed that yeast could effectively ferment OPH even without nutrient addition, revealing the tolerance of yeast to OP toxicity. Because of low xylan (12.4%) and glucan (16%) content in OP, this specific type of OP is not a suitable material for producing only ethanol and thus, bioethanol production should be integrated with production of other value-added products.     

The use of tamarind waste to improve ethanol production from cane molasses

Tamarind wastes such as tamarind husk, pulp, seeds, fruit and the effluent generated during tartaric acid extraction were used as supplements to evaluate their effects on alcohol production from cane molasses using yeast cultures. Small amounts of these additives enhanced the rate of ethanol production in batch fermentations. Tamarind fruit increased ethanol production (9.7%, w/v) from 22.5% reducing sugars of molasses as compared to 6.5% (w/v) in control experiments lacking supplements after 72 h of fermentation. In general, the addition of tamarind supplements to the fermentation medium showed more than 40% improvement in ethanol production using higher cane molasses sugar concentrations. The direct fermentation of aqueous tamarind effluent also yielded 3.25% (w/v) ethanol, suggesting its possible use as a diluent in molasses fermentations. This is the first report, to our knowledge, in which tamarind-based waste products were used in ethanol production. Received 2 April 1998/ Accepted in revised form 13 November 1998     

Acetone, butanol and ethanol production from domestic organic waste by solventogenic clostridia

Domestic organic waste (DOW) was washed and dried to 85 % dryness by VAM (The Netherlands). This material contained 25.1 g glucose, 8.4 g xylose and 5.8 g other monosaccharides/100 g dry matter. Using Mansonite steam explosion and enzymatic hydrolysis, a hydrolysate containing 15.4 g glucose, 2.2 g xylose and 0.8 g other monosaccharides per l was made. Clostridium acetobutylicum DSM 1731 produced 1.5 and C. beijerinckii B-592 0.9 g/l ABE and Clostridium LMD 84.48 1.9 g/l IBE, respectively, from this hydrolysate without further supplementation. Incubation with 2 fold concentrated hydrolysate completely impaired ABE production. After removal of unspecific inhibiting components, the yield of ABE production by Clostridium acetobutylicum DSM 1731 increased about 3 fold as compared to the nontreated hydrolysate. From 4 fold concentrated, partially purified, hydrolysate containing 34.2 g glucose/l, ABE production was 9.3 g/l after 120 h as compared to 3.2 g ABE/I from non-concentrated hydrolysate which contained 12.0 g glucose/l after elution over the same column. The concentration of butyric acid in the fermented hydrolysates was 2.2 and 0.4 g/l, respectively. This reasonably low amount of butyric acid showed that the fermentation had proceeded quite well.     

Immobilization ofSaccharomyces diastaticus on wood chips for ethanol production

Saccharomyces diastaticus cells were immobilized onto beech wood chips of different particle size and three pH values. pH values in the range 5.0–6.0, and 1.84–1.92 mm particle size had a positive effect on the immobilization process. The chosen carrier—1.84 mm-sized wood chips adsorbed 150 mg dry cell mass per g dry carrier mass. The Gibbs free energy and the activation energy for the first (monolayer) and second (multilayer) immobilization stages was 4581, 19090 and 8590 J g mol⁻¹, respectively. The kinetics of immobilized cell systems in ethanol production have been studied in a packed bed-reactor. Ethanol production and the respiration quotient (RQ) were at a maximum at a dilution rate of 0.16/h. The reactor was operated under steady-state conditions for 30 d at the dilution rate 0.16/h.     

Biorefining of platinum group metals from model waste solutions into catalytically active bimetallic nanoparticles

Bacteria can fabricate platinum group metal (PGM) catalysts cheaply, a key consideration of industrial processes and waste decontaminations. Biorecovery of PGMs from wastes is promising but PGM leachates made from metallic scraps are acidic. A two‐step biosynthesis ‘pre‐seeds’ metallic deposits onto bacterial cells benignly; chemical reduction of subsequent metal from acidic solution via the seeds makes bioscaffolded nanoparticles (NPs). Cells of Escherichia coli were seeded using Pd(II) or Pt(IV) and exposed to a mixed Pd(II)/Pt(IV) model solution under H₂ to make bimetallic catalyst. Its catalytic activity was assessed in the reduction of Cr(VI), with 2 wt% or 5 wt% preloading of Pd giving the best catalytic activity, while 1 wt% seeds gave a poorer catalyst. Use of Pt seeds gave less effective catalyst in the final bimetallic catalyst, attributed to fewer and larger initial seeds as shown by electron microscopy, which also showed a different pattern of Pd and Pt deposition. Bimetallic catalyst (using cells preloaded with 2 wt% Pd) was used in the hydrogenation of soybean oil which was enhanced by ~fourfold using the bimetallic catalyst made from a model waste solution as compared to 2 wt% Pd preloaded cells alone, with a similar selectivity to cis C18:1 product as found using a Pd‐Al₂O₃ commercial catalyst.     

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.     

Agro-industrial waste materials and wastewater sludge for rhizobial inoculant production: a review

Inoculating legumes with commercial rhizobial inoculants is a common agriculture practice. Generally, inoculants are sold in liquid or in solid forms (mixed with carrier). The production of inoculants involves a step in which a high number of cells are produced, followed by the product formulation. This process is largely governed by the cost related to the medium used for rhizobial growth and by the availability of a carrier source (peat) for production of solid inoculant. Some industrial and agricultural by-products (e.g. cheese whey, malt sprouts) contain growth factors such as nitrogen and carbon, which can support growth of rhizobia. Other agro-industrial wastes (e.g. plant compost, filtermud, fly-ash) can be used as a carrier for rhizobial inoculant. More recently, wastewater sludge, a worldwide recyclable waste, has shown good potential for inoculant production as a growth medium and as a carrier (dehydrated sludge). Sludge usually contains nutrient elements at concentrations sufficient to sustain rhizobial growth and heavy metals are usually below the recommended level. In some cases, growth conditions can be optimized by a sludge pre-treatment or by the addition of nutrients. Inoculants produced in wastewater sludge are efficient for nodulation and nitrogen fixation with legumes as compared to standard inoculants. This new approach described in this review offers a safe environmental alternative for both waste treatment/disposal and inoculant production.     

SO2-catalysed prehydrolysis of coniferous wood for ethanol production

Summary This paper reports studies of large scale, 1500 kg/h, SO₂-catalysed prehydrolysis of coniferous wood chips, samples then being hydrolyzed by a wood-saccharifying enzyme system followed by fermentation to ethanol in the laboratory. Hemicellulose hydrolysis using SO₂ catalyst (prehydrolysis) was found to be more effective than steam alone (autohydrolysis). Prehydrolysis time was 2 min, with steam pressure at 1.2 to 1.7 MPa (175 to 250 psig), and SO₂ catalyst 2.0 to 2.6% on dry wood. The amount of sugars recovered upon enzyme saccharification of the prehydrolysed wood was about 70% of the weight of the wood. When these combined hemicellulose and cellulose sugars were fermented by a pentose-fermenting strain of yeast,Pichia stipitis R, 372 L ethanol/tonne of (dry) wood was obtained.     

废弃活性污泥中产聚羟基脂肪酸酯菌株Bacillus sp. PB-3的发酵条件优化

通过尼罗红染色法结合荧光显微镜镜检,从废弃活性污泥中分离得到1株高产聚羟基脂肪酸酯(PHAs)的菌株Bacillus sp.PB-3,经气相色谱法鉴定该菌株胞内产物为聚β-羟基丁酸酯(PHB)。对培养基成分及发酵条件优化后,获得最佳培养方案:12 g/L的葡萄糖为C源,2 g/L的牛肉膏为N源,初始pH 7.5,培养基装液量80 mL,转速为200 r/min,37℃培养48 h,PHB质量分数可达菌体干质量的32.09%,比优化前提高30%。     

餐厨垃圾协同剩余污泥发酵产酸的生物过程与影响因素研究进展

资源化利用是应对餐厨垃圾(Kitchen waste,KW)和剩余污泥(Excess sludge,ES)快速增加的有效方法,而厌氧发酵获得挥发性脂肪酸(Volatile fatty acids,VFAs)是其中的重要方式之一,但单一底物限制了VFAs的高效生产.近年来,不同底物厌氧共发酵产生VFAs被广泛研究与应用,...     

Resolving mismatches in the flexible production of ethanol and butanol from eucalyptus wood with vacuum fermentation

Bioprocess and Biosystems Engineering - In flexible ethanol-butanol plants, low tolerance to butanol by solventogenic clostridia (and resulting dilute fermentation) results in considerable number...     

Cellulase-free xylanase production from an alkalophilicBacillus species

An alkalophilicBacillus (NCL-87-6-10, NCIM 2128), with a high productivity for extracellular xylanase (EC 3.2.1.8) and free of cellulase, was isolated from soil containing coconut fibre detritus. When grown on a wheat bran/yeast extract medium in submerged culture for 48 h, it produced 100 to 120 IU of enzyme activity per ml. The crude enzyme consists of two fractions of apparent mol sizes of approx 10.4 and 29 kDa in the proportion of 90:10, as determined by native gel exclusion chromatography. Optimum activity of the xylanase was at 60°C and pH 8.0. A two-fold increase in enzyme activity was obtained when reducing agents, thioethanol and dithiothreitol, were included in the assay.NCL Communication No. 5381.     

Ethanol production of semi-simultaneous saccharification and fermentation from mixture of cotton gin waste and recycled paper sludge

Ethanol production from the steam-exploded mixture of 75% cotton gin waste and 25% recycled paper sludge in various conditions was investigated by semi-simultaneous saccharification and fermentation (SSSF) consisting of a pre-hydrolysis and a simultaneous saccharification and fermentation (SSF). Four cases were studied: 24-h pre-hydrolysis + 48-h SSF (SSSF 24), 12-h pre-hydrolysis + 60-h SSF (SSSF 12), 72-h SSF, and 48-h hydrolysis + 24-h fermentation (SHF). The ethanol concentration, yield, and productivity of SSSF 24 were higher than those of the other operations. A model of SSF was used to simulate the data for four components in SSF. The analysis of the reaction rates of cellobiose, glucose, cell, and ethanol using the model and the parameters from the experiments showed that there was a transition point of the rate-controlling step at which the cell growth control in the initial 2 h was changed to the cellobiose reaction control in later period during ethanol production of SSF from the mixture.