Column cellulose hydrolysis reactor: An efficient cellulose hydrolysis reactor with continuous cellulase recycling

Summary The use of a column cellulose hydrolysis reactor with continuous enzyme recycling was demonstrated by incorporating a continuous ultrafiltration apparatus at the effluent end of the column reactor. Using this setup, over 90% (w/v) cellulose hydrolysis was achieved, resulting in an average sugar concentration of 6.8% (w/v) in the effluent stream. The output of the system was 1.98 g of reducing sugar/l/h with a ratio of 87% (w/v) of the reducing sugars being monomeric sugars. Batch hydrolysis reactors were less effective, resulting in 57% (w/v) of the cellulose being hydrolyzed. The output of the batch reactor was 1.33 g of reducing sugar/l/h with similar product concentrations and percentage of monomeric sugars. The ratio of reducing sugar/filter paper unit of cellulase activity for the column method was 69.1 mg/U as compared to only 21.2 mg/U for the batch reactor.     

High efficiency degradation of tetrahydrofuran (THF) using a membrane bioreactor: identification of THF-degrading cultures of<Emphasis Type="Italic"> Pseudonocardia</Emphasis> sp. strain M1 and<Emphasis Type="Italic"> Rhodococcus ruber</Emphasis> isolate M2

A mixed microbial culture capable of growing aerobically on tetrahydrofuran (THF) as a sole carbon and energy source was used as the inoculum in a 10 l working volume membrane bioreactor. Following start-up, the reactor was operated in batch mode for 24 h and then switched to continuous feed with 100% biomass recycle. On average, greater than 96% of THF fed to the reactor was removed during the 8-month study. THF loading rates ranged from 0.62 to 9.07 g l^–1 day^–1 with a hydraulic retention time of 24 h. THF concentrations as high as 800 mg/l were tolerated by the culture. Biomass production averaged 0.28 kg total suspended solids/kg chemical oxygen demand removed, i.e., comparable to a conventional wastewater treatment process. Periodic batch wasting resulted in a solids retention time of 7–14 days. Reactor biomass typically ranged from 4 to 10 g/l volatile suspended solids and the effluent contained no solids. Pure THF-degrading cultures were isolated from the mixed culture based on morphological characteristics, Gram-staining and THF degradation. Based on 16S rDNA analysis the isolates were identified as Pseudonocardia sp. M1 and Rhodococcus ruber M2.     

The effect of temperature and effluent recycle rate on hydrogen production by undefined bacterial granules

Biohydrogen production in an anaerobic fluidized granular bed bioreactor was strongly dependent on temperature and effluent recycle rates. At 45 °C as the effluent recycle rate was increased from 1.3 to 3.5 L/min, the total H? output for the bioreactor increased from 10.6 to 43.2 L/h. Volumetric H(2) productivity also increased from 2.1 to 8.7 L H?/L/h. At 70°C as the effluent recycle was increased from 1.3 to 3.5 L/min, the total H? output for the bioreactor increased from 13.8 to 73.8L/h. At 70 °C volumetric H(2) productivities increased from 2.8 to 14.8L H?/L/h as the effluent recycle rate was increased from 1.3 to 3.5 L/min. At 45 °C % H? was 45% and reached 67% at 70 °C. Maximum hydrogen yields at 45 °C were 1.24 and 2.2 mol H?/mol glucose at 70 °C.     

The use of effluent from grass silage in the diet of finishing pigs. I. Variation in composition of effluents

Effluent was collected in the fresh state from 3 batches of silage made from ryegrass, the dry matter content of the silages ranging from 203 to 265 g/kg. Samples of effluent were collected daily, stored at ?20°C and later bulked to form weekly composite samples. The pH ranged from 3.24 to 3.82, dry matter (DM) from 61.5 to 109.7 g/kg, crude protein from 190 to 337 g/kg DM and ash from 149 to 217 g/kg DM. These values were not related to source of effluent except for dry matter; the higher the dry matter in the silage the higher the dry matter in the corresponding effluent.On average, effluent contained 266 g crude protein/kg DM, of which 176 g was contributed by amino acids excluding tryptophan. The mean content of the more important acids per kg DM was lysine 11.2 g, methionine plus cystine 5.9 g and threonine 10.6 g. Lysine varied with source of effluent and also tended to decrease with increasing time from commencement of flow. The overall mean levels of mineral elements were: calcium, 18.6 g/kg DM; phosphorus, 10.6 g/kg DM; magnesium, 4.4g/kg DM; sodium, 7.4 g/kg DM; potassium, 23.4 g/kg DM; managanese, 378 mg/kg DM; iron, 1965 mg/kg DM; copper, 17 mg/kg DM; zinc 670 mg/kg DM. Lactic acid always exceeded the total volatile fatty acid content of the effluents and of the volatile fatty acids, acetic acid always predominated. The mean total acid content was 118 g/kg DM, which subtracted from a calculated nitrogen-free extract value of 538 g/kg DM indicated a total carbohydrate content of effluent of 420 g/kg DM.     

硫酸盐还原一甲烷化两相厌氧消化系统运行工艺条件的研究

以合成废水为基质,研究了采用硫酸盐还原-甲烷化两相厌氧新型工艺处理含高浓度硫酸盐有机废水的系统运行工艺条件.结果表明,酸化-硫酸盐还原反应器的适宜pH为6.5-7.0;500mg/l的S~(2-)使SRB的硫酸盐还原活性下降;208mg/l的[H_2S]_L抑制MPB活性的95.4%;推导出估算气提塔出水回流比R的模型;以得到的工艺条件为依据处理了含19200mg/1的SO_4~(2-)和29400mg/l COD的味精废水.     

Preliminary studies on continuous chromium(VI) biological removal from wastewater by anaerobic-aerobic activated sludge process

The long-term continuous chromium(VI) removal from synthetic wastewater affected by influent hexavalent chromium (Cr(VI)) and glucose concentrations were studied with an anaerobic-aerobic activated sludge process. It was observed that before activated sludge was acclimated, the chromium in the effluent increased immediately as the influent chromium increased. However, both Cr(VI) and total chromium (TCr) in the effluent significantly decreased after acclimation. In the acclimated activated sludge, the chromium removal efficiency was 100% Cr(VI) and 98.56% TCr at influent Cr(VI) levels of 20 mg/day, 100% Cr(VI) and 98.92% TCr at influent Cr(VI) levels of 40 mg/day, and 98.64% Cr(VI) and 97.16% TCr at influent Cr(VI) levels of 60 mg/day. The corresponding effluent Cr(VI) and TCr concentrations were 0 and 0.012 mg/l, 0 and 0.018 mg/l, and 0.034 mg/l and 0.071 mg/l, respectively. When the influent glucose increased from 1125 to 1500 mg/l at influent Cr(VI) dosage of 60 mg/day, the Cr(VI) and TCr removal efficiency with the acclimated activated sludge improved from 98.64% and 97.16% to 100% and 98.48%, respectively, and the chromium concentration in the effluent decreased from 0.034 mg/l of Cr(VI) and 0.071 mg/l of TCr to 0 (Cr(VI)) and 0.038 mg/l (TCr). The effluent COD and turbidity was around 40 mg/l and 0, respectively, after the activated sludge was acclimated. Further studies showed that after the activated sludge was acclimated, its specific dehydrogenases activity (SDA) and protein contents increased. The SDA and protein increased respectively 15% and 10% when influent Cr(VI) increased from 20 to 60 mg/day.     

Biological decomposition of dichloromethane from a chemical process effluent

The application of specialized microorganisms to treat dichloromethane (DM) containing process effluents was studied. An aerobic fluidized bed reactor with a working volume of 801 filled with sand particles as carriers for the bacteria was used. Oxygen was introduced into the recycle stream by an injector device. DM was monitored semi-continuously. A processor controlled the feed volume according to the DM effluent concentration. Mineralization rates of 12 kg DM/m_bioreactor ³ · d were reached within about three weeks using synthetic wastewater containing 2000 mg/l DM as single carbon compound. DM from process water of a pharmaceutical plant was reduced from about 2000 mg/l in the feed to below 1 mg/l in the effluent at volumetric loading rates of 3 to 4 kg DM/m_bioreactor ³ · d. Degradation of wastewater components like acetone and isopropanol were favoured, thus making the process less attractive for waste streams containing high amounts of DOC other than of DM. DM concentrations of up to 1000 mg/l were tolerated by the immobilized microorganisms and did not influence their DM degradation capacity. The ability to mineralize DM was lost when no DM was fed to the reactor for 10 days.     

Kinetics of ethanol production by immobilized Kluyveromyces marxianus cells at varying sugar concentrations of Jerusalem artichoke juice

Summary Kinetics of ethanol fermentation at varying sugar concentrations of Jerusalem artichoke tuber extract has been studied using Kluyveromyces marxianus cells immobilized in calcium alginate gel beads. A maximum ethanol concentration of 111 g/l was achieved at an initial sugar concentration of 260 g/l in 20 hours, when the immobilized cell concentration in the calcium alginate beads was 53.3 g dry wt./l bead volume. Ethanol yield remained almost unaffected by initial sugar concentration up to 250 g/l and was found to be about 88% of the theoretical. Maximum rate of ethanol production decreased from 22.5 g ethanol/l/h to 10.5 g ethanol/l/h while the maximum rate of total sugars utilization decreased from 74.9 g sugars/l/h to 28.5 g sugars/l/h as the initial substrate concentration was increased from 100 to 300 g/l. The concentration of free cells in the fermentation broth was low.     

Effect of oleic acid on the production of ethanol and fructose from glucose/fructose mixtures in an immobilized cell reactor

Saccharomyces cerevisiae ATCC 39859 was immobilized onto small cubes of wood to produce ethanol and very enriched fructose syrup from glucose/fructose mixtures through the selective fermentation of glucose. A maximum ethanol productivity of 21.9 g/l-h was attained from a feed containing 9.7% (w/v) glucose and 9.9% (w/v) fructose. An ethanol concentration, glucose conversion and fructose yield of 29.6 g/l, 62% and 99% were obtained, respectively. This resulted in a final fructose/glucose ratio of 2.7. At lower ethanol productivity levels the fructose/glucose ratio increases, as does the ethanol concentration in the effluent. The addition of 30 mg/l oleic acid to the medium increased the ethanol productivity and its concentration by 13% at a dilution rate of 0.74 h^?1.     

Palm oil mill effluent treatment by a tropical marine yeast

Palm oil mill effluent (POME), from a factory site in India contained about 250,000 mg l(-1) chemical oxygen demand (COD), 11,000 mg l(-1) biochemical oxygen demand, 65 mg l(-1) total dissolved solids and 9000 mg l(-1) of chloroform-soluble material. Treatment of this effluent using Yarrowia lipolytica NCIM 3589, a marine hydrocarbon-degrading yeast isolated from Mumbai, India, gave a COD reduction of about 95% with a retention time of two days. Treatment with a chemical coagulant further reduced the COD and a consortium developed from garden soil clarified the effluent and adjusted the pH to between 6 and 7. The complete treatment reduced the COD content to 1500 mg l(-1) which is a 99% reduction from the original.     

Incorporation of ultrasonic cell disintegration into a membrane bioreactor for zero sludge production

For the prevention of excess sludge production from a membrane bioreactor (MBR), an ultrasonic cell disintegration process was incorporated. The results of this study showed that excess sludge production could be prevented using an ultrasound hybrid (MBR-US) system at an organic loading of around 0.91 kg BOD₅/m³ per day. Under the same organic loading rate, the mixed liquor suspended solid (MLSS) of MBR-US system was maintained at 7000–8000 mg/l while the MLSS of a conventional MBR increased from 7000 to 13,700 mg/l during the experimental period. While sludge production was completely prevented, the effluent quality of the MBR-US system slightly deteriorated. The additional organic loading caused by disintegrated sludge return was considered to be a reason. With sonication the volume of the average particle size of the sludge in the aeration tank decreased from 132 to 95 μm. In the MBR-US system, around 25–30% of total phosphorus removal was achieved without sludge removal from the aeration tank.     

Effect of effluent recycling and shock loading on the biodegradation of complex phenolic mixture in hybrid UASB reactors

This study describes the feasibility of anaerobic treatment of synthetic coal wastewater using four identical 13.5L (effective volume) bench scale hybrid up flow anaerobic sludge blanket (HUASB) reactors (R1, R2, R3 and R4) under mesophilic (27+/-5 degrees C) conditions. Synthetic coal wastewater with an average chemical oxygen demand (COD) of 2240 mg/L and phenolics concentration of 752 mg/L was used as substrate. Effluent recirculation was employed at four different effluent to feed recirculation ratios (R/F) of 0.5, 1.0, 1.5 and 2.0 for 100 days to study the effect of recirculation on the performance of the reactors. Phenolics and COD removal was found to improve with increase in effluent recirculation. An effluent to feed recycle ratio of 1.0 resulted in maximum removal of phenolics and COD. Phenolics and COD removal improved from 88% and 92% to 95% each, respectively. The concentration of volatile fatty acids in the effluent was lower than the influent when effluent to feed recirculation was employed. Effect of shock loading on the reactors revealed that phenolics shock load up to 2.5 times increase in the normal input phenolics concentration in the form of continuous shock load for 4days did not affect the reactors performance irreversibly.     

High solids fermentation of hydrolysates of wheat starch B in a continuous dynamic immobilized biocatalyst bioreactor

Summary A simple and efficient method of conversion of wheat starch B to ethanol was investigated. Employing a two-stage enzymatic saccharification process, 95% of the wheat starch was converted to fermentable sugars in 40 h. From 140 g/l total sugars in the feed solution, 63.6 g/l ethanol was produced continuously with a residence time of 3.3 h in a continuous dynamic immobilized biocatalyst bioreactor by immobilized cells ofSaccharomyces cerevisiae. The advantages and the application of this bioreactor to continuous alcoholic fermentation of industrial substrates are presented.     

Kinetics of sugars consumption and ethanol inhibition in carob pulp fermentation by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> in batch and fed-batch cultures

The waste materials from the carob processing industry are a potential resource for second-generation bioethanol production. These by-products are small carob kibbles with a high content of soluble sugars (45–50%). Batch and fed-batch Saccharomyces cerevisiae fermentations of high density sugar from carob pods were analyzed in terms of the kinetics of sugars consumption and ethanol inhibition. In all the batch runs, 90–95% of the total sugar was consumed and transformed into ethanol with a yield close to the theoretical maximum (0.47–0.50 g/g), and a final ethanol concentration of 100–110 g/l. In fed-batch runs, fresh carob extract was added when glucose had been consumed. This addition and the subsequent decrease of ethanol concentrations by dilution increased the final ethanol production up to 130 g/l. It seems that invertase activity and yeast tolerance to ethanol are the main factors to be controlled in carob fermentations. The efficiency of highly concentrated carob fermentation makes it a very promising process for use in a second-generation ethanol biorefinery.     

Degradation of 4-chlorophenol in UASB reactor under methanogenic conditions

Treatment of simulated wastewater containing 40 mg/l of 4-chlorophenol (4-CP) was carried out in an upflow anaerobic sludge blanket (UASB) reactor under methanogenic condition. The performance of this test UASB reactor was evaluated in terms of 4-CP removal. Hydraulic retention time (HRT) and substrate:co-substrate ratio for the 4-CP removal was optimized by varying the influent flow rate (13-34.7 ml/min) and sodium acetate concentration (2-5 g/l), respectively. A control UASB reactor, which was not exposed to 4-CP was also operated under similar conditions. Organic loading rate (OLR) was varied in the range of 2-5.3 kg/m(3)/d and 1.7-4.2 kg/m(3)/d, respectively, for HRT and substrate:co-substrate ratio studies, respectively. The optimum HRT and substrate:co-substrate ratio for the removal of 4-CP was 12h and 1:75, respectively. Removal of 4-CP achieved at optimum HRT and substrate:co-substrate ratio was 88.3+/-0.7%. Removal of 4-CP occurred through dehalogenation and caused increase in chloride ion concentration in the effluent by 0.23-0.27 mg/mg 4-CP removed. The ring cleavage test showed the ortho mode of ring cleavage of 4-CP. Change in the elemental composition of the anaerobic biomass of UASB reactors was observed during the study period. Concentration of Ca(2+) increased in the biomass and this could be attributed to the biosoftening. Specific methanogenic activity of the sludge of control and test UASB reactor was 0.832 g CH(4) COD/g VSS d and 0.694 g CH(4) COD/g VSS d, respectively.     

Utilisation of tomato pomace as a substrate for the production of vitamin B12--a preliminary appraisal

The cellulose fraction in tomato pomace was hydrolysed using Trichoderma reesei, and the resultant sugars were fermented with Propionibacterium shermanii to produce vitamin B12. A multifactorial experiment revealed that aeration of the culture of T. reesei gave substantial improvements in cellulase activity as did higher concentrations of available nitrogen, but a rapid drop in pH appeared to inhibit extensive hydrolysis; after 14 days, the maximum level of cellulose degradation was only 34.4% of the total available, and the highest level of reducing sugars achieved was 15 g l(-1). When flasks with the latter concentration of reducing sugars were inoculated with P. shermanii, 11.1 mg l(-1) of B12 were produced under optimum conditions. If the degree of hydrolysis of the cellulose could be increased, then sufficient vitamin B12 might be generated to justify extraction but, even if purification does not prove to be economically feasible, a fermented tomato pomace (dried) with 50-55 mg kg(-1) or more of B12 could prove a useful feedstuff for animals.     

Anaerobic on-site treatment of kitchen waste in combination with black water in UASB-septic tanks at low temperatures

Anaerobic on-site treatment of a mixture of black water and kitchen waste (BWKW) was studied using two-phased upflow anaerobic sludge blanket (UASB) septic tanks at the low temperatures of 20 and 10 degrees C. Black water (BW) was also treated alone as reference. The two-phased UASB-septic tanks removed over 95% of total suspended solids (TSS) and 90% of total chemical oxygen demand (COD(t)) from both BWKW (effluent COD(t) 171-199mg/l) and BW (effluent COD(t) 92-100mg/l). Also, little dissolved COD (COD(dis)) was left in the final effluents (BW 48-70mg/l; BWKW 110-113mg/l). Part of total nitrogen (N(tot)) was removed (BW 18% and BWKW 40%) and especially at 20 degrees C ammonification was efficient. A two-phased process was required to obtain the high removals with BWKW at 10 degrees C, while with BW a single-phased process may have sufficed even at 10 degrees C. BWKW also produced more methane than BW alone. Sludge in phases 1 of BW and BWKW treatment was not completely stabilised after 198d of operation.     

The use of effluent from grass silage in the diet of finishing pigs. II. Assessment of nutritive value of fresh and stored effluent

Freshly collected effluent was treated with 2 ml formalin per litre and used to replace 150 g/kg of the dry matter of an all-meal control diet of bacon pigs. Diets containing effluent from either unwilted or wilted crops were compared with the control diet which was also given wet by adding water. Liveweight gains of 10 pigs per treatment from 65 to 86 kg on diets containing effluents from unwilted and wilted crops and on the control diet were 753, 715 and 719 ± 16.8 g/day, respectively, and in the same order feed conversion ratios (corrected to dry matter content of the control diet) were 2.94, 3.10 and 3.07 ± 0.075. None of these differences were significant. There were no significant differences in killing-out yield, in hardness of subcutaneous back-fat when measured by a penetrometer or in abnormal odour rating of subcutaneous back-fat.Formalin at levels of 1 and 2 ml/l and formic acid at levels of 1, 2 and 6 ml/l were added as potential preservatives to 1000 ml quantities of freshly collected silage effluent, which was then stored at 23°C. The 2 ml/l level of formalin and 6 ml/l level of formic acid prevented mould growth for 26 and 19 days, respectively.Freshly collected effluent was stored for 3.5, 14, 28, 56, 112 and 240 days after treatment, with formalin at the rate of 3 ml/l, and used in a pig-feeding trial. Pigs were fed either on a control all-meal diet or an equal dry matter intake of 150 g/kg effluent DM and 850 g/kg meal DM.A total of 120 animals were individually penned and fed twice daily on the experimental diets from 33 kg to slaughter at 82 kg liveweight. Overall mean liveweight gains for effluent and control diets were 646 and 656 ± 7.5 g/day, respectively, and the corresponding feed conversion ratios (DM basis) were 2.69 and 2.64 ± 0.030, neither of the differences being significant. Animal performance did not deteriorate with increasing period of effluent storage. No significant differences were found in carcase lean, back-fat thickness nor hardness of back-fat.A digestibility study was carried out on freshly collected effluent from another source. The level of dietary inclusion was equal to that in the previous experiments and the digestibility of dry matter was 0.831 and 0.819, and of nitrogen 0.822 and 0.827 for the control and effluent diets, respectively. A value of 11.4 MJ/kg dry matter was calculated by difference for the digestible energy of this effluent. In a further digestibility trial, digestible energy values of 14.6 and 14.2 MJ/kg dry matter were calculated by difference for effluents stored for 3.5 and 300 days, respectively.     

Optimization of acid hydrolysis from the hemicellulosic fraction of Eucalyptus grandis residue using response surface methodology

Biotechnological conversion of biomass into fuels and chemicals requires hydrolysis of the polysaccharide fraction into monomeric sugars. Hydrolysis can be performed enzymatically and with dilute or concentrate mineral acids. The present study used dilute sulfuric acid as a catalyst for hydrolysis of Eucalyptus grandis residue. The purpose of this paper was to optimize the hydrolysis process in a 1.4 l pilot-scale reactor and investigate the effects of the acid concentration, temperature and residue/acid solution ratio on the hemicellulose removal and consequently on the production of sugars (xylose, glucose and arabinose) as well as on the formation of by-products (furfural, 5-hydroxymethylfurfural and acetic acid). This study was based on a model composition corresponding to a 2(3) orthogonal factorial design and employed the response surface methodology (RSM) to optimize the hydrolysis conditions, aiming to attain maximum xylose extraction from hemicellulose of residue. The considered optimum conditions were: H(2)SO(4) concentration of 0.65%, temperature of 157 degrees C and residue/acid solution ratio of 1/8.6 with a reaction time of 20 min. Under these conditions, 79.6% of the total xylose was removed and the hydrolysate contained 1.65 g/l glucose, 13.65 g/l xylose, 1.55 g/l arabinose, 3.10 g/l acetic acid, 1.23 g/l furfural and 0.20 g/l 5-hydroxymethylfurfural.     

Production of γ-linolenic acid by Cunninghamella echinulata cultivated on glucose and orange peel

A newly isolated strain of Cunninghamella echinulata grown on glucose produced significant quantities of biomass and cellular lipids in media with high C/N ratio. The oil yield from glucose consumed increased after nitrogen exhaustion in the growth medium, but gamma-linolenic acid (GLA) content in cellular oil systematically decreased during the lipid accumulation process. When lipid accumulation was completed, GLA concentration in the cellular lipids progressively increased. The highest GLA production (720 mg/l) was achieved in medium with a C/N ratio equal to 163. C. echinulata was also able to grow on orange peel. The C/N ratio in the orange peel decreased from 50 to 26 during solid-state fermentation. Maximum oxygen uptake was observed during assimilation of reducing sugars, whereas a polygalacturonase activity was detected after reducing sugars had been exhausted. The maximum GLA production was 1.2-1.5 mg/g of fermented peel, calculated on a dry weight basis. After enrichment of the pulp with inorganic nitrogen and glucose, an increase in the production of oil and GLA was observed.