Control/promotion of the refuse methanogenic fermentation

Although practiced for more than 7 millennia, the landfill disposal of refuse has, as yet, with few exceptions, been merely regarded as a low-cost disposal option and its exploitation potential has been largely ignored. Today, however, a number of possibilities are under consideration including the production of energy, chemical feedstock, value-added chemicals, carbon dioxide and protein; the use of refuse as an anaerobic filter for the co-disposal of industrial wastewater and sludge; and the restoration of impoverished soils by fresh or composted refuse addition. Development of these technologies, however, necessitates a comprehensive understanding of the fundamental microbiology and biochemistry of refuse catabolism. Existing fundamental knowledge underpinning these technologies will be considered in a series of review articles. In the first, control/exploitation of the solid-state refuse methanogenic fermentation is examined with specific reference to the effects of first-tier variable manipulations.     

Preliminary investigation of the influence of pH on the solid-state refuse methanogenic fermentation

Laboratory refuse columns and bottle cultures were used to examine the responses of the interrelated metabolic processes of acid metabolism, solvent metabolism and methanogenesis of the solid-state refuse fermentation to single initial additions of exogenous buffering capacity. Refuse samples poised at neutral and alkaline pH values, by the addition of 0.2 mol/1 phosphate buffer, were found to promote acid-ogenesis to such an extent that methanogenesis was inhibited. The same inhibition was also apparent in the presence of acid pH regimes which were initially characterized by the accumulation of solvents. The possible implications of controlling pH by adding buffer to promote and exploit the refuse fermentation are discussed.     

Interactive effects of temperature and cf4 o- cf3 cresol co-disposal on the methanogenic fermentation of refuse

The influence of temperature on both o- cresol biodegradation and methanogenic refuse decomposition was investigated. Maximum o- cresol attenuation was recorded from 25 to 37°C. Mesophilic and thermophilic sulphate-reducing bacterial (SRB) activity was observed, but thermophilic methanogenesis was not recorded. Maximum methane release and SRB activity was recorded at 25–37°C, and ≥30°C, respectively. Optimum conditions for acetate utilization were similar to those for methanogenesis, but propionate degradation apparently depended on SRB activity. Propionate degradation was recorded under thermophilic conditions, even in the absence of methanogenesis, although the optimum temperature was 37°C. When SRB were inhibited, at temperatures ≤25°C, no significant propionate catabolism was observed.     

Solid-state fermentation of maple wood by Polyporus anceps

Summary Solid-state fermentations of alkali-treated maple wood shavings were carried out at 30°C in three types of static tray fermenters using Polyporus anceps. Comparison of the fermentation products after 40 days showed a recirculating tower bioreactor (RTB) to be more effective for the production of protein and the consumption of substrate than either a shallow or deep static tray fermentation vessel. Use of the RTB resulted in 70% substrate utilization and a residue containing 17% crude protein.     

Acidogenic and methanogenic fermentation of causticized straw

The effects of pretreatment process variables [straw concentration between 20 and 90 kg volatile solids (VS)/m(3), temperature between 30 and 85 degrees C, and alkaline dosage between 0 and 80 g NaOH/kg VS] on acidogenesis and methanogenesis were investigated. Rates of acidogenesis and methanogenesis were determined using firstorder kinetics, and ultimate acid and methane yields were measured. The acid yield was not affected by pretreatment concentration or temperature, but increased as alkaline dosage increased. The acidogenesis rate was not affected by pretreatment temperature or alkaline dosage, but decreased as the substrate concentration increased. This decrease in the acidogenesis rate was attributed to a decrease in the inoculum: substrate ratio as the substrate concentration increased. The methane yield and methanogenesis rate were not affected by pretreatment substrate concentration or temperature, and both increased with alkaline dosage up to about 40 g NaOH/kg VS, then remained relatively constant above 40 g NaOH/kg VS.     

The microbiological basis of process control in methanogenic fermentation of soluble wastes

The essential requirement for anaerobic digestion of industrial wastes is that the process should operate reliably at high performance. In the digestion of dilute, soluble wastes it is necessary to retain the active biomass within the digester at short liquid retention times for the process to be economically feasible and this is reflected in digester design. Performance of digesters can only be assessed by interpretation of measurable parameters such as pH₂, E_h, pH, volatile fatty acid concentrations, temperature, gas production, biomass content and feed rate and composition. The effects of changes in these parameters on the microbiology of methanogenic digestion and the application of this knowledge in control of the process is discussed.     

Solid-state fermentation of natural birch lignin by Phanerochaete chrysosporium

A strain of white rot fungus, Phanerochaete chrysosporium Burds. ME446, has been characterized with respect to the extent and rate of Betula nigrificans lignin and non-lignin conversion by solid-substrate fermentation for different culture conditions. Moisture content, inoculum density, nitrogen supplementation and autoclaving of birch solids significantly affected lignin conversion rates and yields in 20 day fermentations. Oxygen favoured lignin over non-lignin conversion at partial pressures of 1.0 atm. Oxygen pressures of 2.0 atm severely inhibited both lignin and non-lignin conversions. Carbon dioxide partial pressures of 0.25, 0.5 and 1.0 atm at oxygen pressures of 1.0 atm increasingly inhibited both lignin and non-lignin conversion rates and yields. The results of these studies demonstrate the effects of major process variables and suggest a need to control the gas environment for process optimization.     

莲子草假隔链格孢SF 193固体发酵培养基的筛选及其对空心莲子草的控制效果

【背景】空心莲子草是一种源于南美洲且正在我国不断传播的外来入侵植物。莲子草假隔链格孢是空心莲子草的强致病菌,能引起空心莲子草茎叶发病,抑制空心莲子草生长。【方法】选择以麦麸、大米、玉米芯粉、玉米粉、稻秸秆粉为基料,棉籽壳、稻秕壳和大豆粉为辅料,按照一定质量比配制固体培养基,筛选适合莲子草假隔链格孢SF-193大量生产的有效组分;同时研究培养基含水量和6种金属离子对SF-193菌落生长的影响。【结果】在以大米和大豆粉质量比为3:1和5:1的培养基上SF-193菌落面积最大,其次为大米和棉籽壳质量比为5:1的培养基。在含水量为20%和30%的培养基上SF-193菌落面积显著大于其他培养基。Mg2+和Mn2+对SF-193菌落生长影响较小,Zn2+对SF-193菌落生长具有显著的抑制作用,而SF-193菌落在含Cu2+和Fe3+的培养基上不能生长。田间控草试验表明,固体发酵生产的菌粉对空心莲子草的致病性显著高于液体菌,用量为50g.m-2时,10d后空心莲子草的病情指数达86.1。【结论与意义】利用固体培养基发酵生产的莲子草假隔链格孢对空心莲子草的防除效果显著优于液体发酵。因此,莲子草假隔链格孢SF-193固体发酵菌粉可能在生物防治空心莲子草方面具有重要作用。     

Solid-state ethanol fermentation by means of inert gas circulation

A new method for solid-state ethanol fermentation (the SSEF system) was experimented on for the ethanol production from solid starchy materials, where a packedbed-type fermentor was used. Both cultivation of Aspergillus saitoi and enrichment of a saccharifying enzyme were effective for hydrolysis of the starch. Ethanol production was set in by a form of parallel fermentation using a respiration-deficient mutant of Saccharomyces cerevisiae. Produced ethanol was simultaneously stripped by circulating inert gas and separated in a condenser. Average ethanol concentration in the condensate was over 200 g/L, and over 90% of produced ethanol was recovered from the packed bed during 15 or 16 days of stripping. The fermentation efficiency was about 80%, which was evaluated much higher than those of conventional solid-state fermentations. The residue had lesser volume and a higher solids content compared with the distillery wastewaters of conventional liquid-state fermentations. This means an advantage for the treatment and the effective conversion of the residue into fetilizers or animal feeds.     

Effects of o-cresol co-disposal and pH on the methanogenic degradation of refuse

SULISTI, I.A. WATSON-CRAIK AND E. SENIOR. 1996. Both maximum o -cresol degradation and activity of sulphate-reducing bacteria (SRB) were observed at refuse pH values between 7.0 and 8.0. Optimum pH values for methane release were between 6.5 and 7.5. Partial inhibition of methane production was recorded at pH 5.7, 6.0 and 8.0, whilst sulphate reduction was inhibited partially at pH values 5.7–6.5. Both sulphate reduction and methanogenesis were completely inhibited in refuse with initial pH 4.0. The catabolism of acetate occurred under similar conditions to methane production, and was promoted at pH 6.5–7.5. It appeared that propionate oxidation depended upon the activities of SRB. Optimum conditions for the metabolism of propionate and other volatile fatty acids were between pH 7.0 and 8.0.     

On-line monitoring of the methanogenic fermentation by measurement of culture fluorescence

Summary Real-time on-line fluorescence measurements of the coenzymes NAD(P)H and F₄₂₀ were evaluated as indicators of stability in a glucose-fed anaerobic methanogenic digester. A probe designed forin situ fluorimetric measurement of NAD(P)H provided an assessment of activity of the total microbial community, while the response of a fluorescence probe designed to measure coenzyme F₄₂₀ correlated well with methanogenic activity. The two fluorescence-monitoring probes responded directly to fermentation imbalance during periods of substrate overloading and corresponded to traditional offline measurements, suggesting that the probes may be suitable candidates for inclusion in an on-line process control system for anaerobic digestion.Florida Agricultural Experimental Station, Journal Series no. R-00326     

The membraneless bioelectrochemical reactor stimulates hydrogen fermentation by inhibiting methanogenic archaea

The membraneless bioelectrochemical reactor (Ml-BER) is useful for dark hydrogen fermentation. The effect of the electrochemical reaction on microorganisms in the Ml-BER was investigated using glucose as the substrate and compared with organisms in a membraneless non-bioelectrochemical reactor (Ml-NBER) and bioelectrochemical reactor (BER) with a proton exchange membrane. The potentials on the working electrode of the Ml-BER and BER with membrane were regulated to ?0.9 V (versus Ag/AgCl) to avoid water electrolysis with a carbon electrode. The Ml-BER showed suppressed methane production (19.8?±?9.1 mg-C·L^?1·day^?1) and increased hydrogen production (12.6?±?3.1 mg-H·L^?1·day^?1) at pH_out 6.2?±?0.1, and the major intermediate was butyrate (24.9?±?2.4 mM), suggesting efficient hydrogen fermentation. In contrast, the Ml-NBER showed high methane production (239.3?±?17.9 mg-C·L^?1·day^?1) and low hydrogen production (0.2?±?0.0 mg-H·L^?1·day^?1) at pH_out 6.3?±?0.1. In the cathodic chamber of the BER with membrane, methane production was high (276.3?±?20.4 mg-C·L^?1·day^?1) (pH_out, 7.2?±?0.1). In the anodic chamber of the BER with membrane (anode-BER), gas production was low because of high lactate production (43.6?±?1.7 mM) at pH_out 5.0?±?0.1. Methanogenic archaea were not detected in the Ml-BER and anode-BER. However, Methanosarcina sp. and Methanobacterium sp. were found in Ml-NBER. Prokaryotic copy numbers in the Ml-BER and Ml-NBER were similar, as were the bacterial community structures. Thus, the electrochemical reaction in the Ml-BER affected hydrogenotrophic and acetoclastic methanogens, but not the bacterial community.     

里氏木霉306产t-PA固态发酵条件的研究

对基因工程菌株里氏木霉(Trichodermareesei)306生物合成组织型纤溶酶原激活剂(t-PA)的固态发酵培养基成分和发酵条件进行了研究;分析了发酵过程中t-PA的生成、总糖的消耗和菌体生长的规律。在优化的固体发酵条件下,t-PA的最大酶活是924.63IU/g干重培养基,较初始条件下提高了5倍。通过浅盘进行了放大实验,最大酶活为983.64IU/g干重培养基,t-PA合成速率为:13.66IU/g干重培养基.h,较三角瓶固态发酵最高产酶提高了6.38%,产酶速率提高了24.07%。     

Removal of PO4 and NH4 from wastewaters by UASB methanogenic fermentation

The removal of PO₄ and NH₄ from wastewaters was investigated by stimulating the formation of precipitates containing PO₄ and NH₄ in granulated sludge in UASB methanogenic fermentation. In a synthetic wastewater containing volatile fatty acids, the removal efficiencies of PO₄ and NH₄ were 85 (influent=406 mg/l) and 60% (influent=100 mg/l), respectively, when 8 mM Ca and 8 mM Mg were added in the influent. In a heat-treated liquor of sewage sludge, a PO₄ removal efficiency of 70% (influent=53 mg/l) was achieved by the addition of 2 mM Ca and 3.5 mM Mg; removal of NH₄, however, was not observed during the experimental periods.     

Improvement of the kirromycin fermentation by resin addition

The kirromycin yield ofActinoplanes sp A8924 was improved from 30–50 mg L^–1 to 350 mg L^–1 by mutant selection and medium optimization. The incorporation of polystyrenic resins into the fermentations promoted a further fourfold enhancement of kirromycin productivity to 1500 mg L^–1. The positive effect of resin addition appears to be due to removal of kirromycin from the fermentation broth because kirromycin's minimal inhibitory concentration against the producing strain remained atca 350 mg L^–1.     

A comprehensive model of simultaneous denitrification and methanogenic fermentation processes

The denitrification process was incorporated into the IWA Anaerobic Digestion Model No. 1 (ADM1) in order to account for the effect of denitrification on the methanogenic fermentation process. The model was calibrated and optimized using previously published experimental data and kinetic parameter values obtained with a mixed, mesophilic (35°C) methanogenic culture. Model simulations were used to predict the effect of nitrate reduction on the methanogenic fermentation process in batch, semi‐continuous, and continuous flow reactors experiencing operational changes and/or system disturbances. The extended model clearly revealed the importance of substrate competition between denitrifiers and non‐denitrifiers as well as the impact of N‐oxide inhibition on process interactions between fermentation, methanogenesis, and denitrification. Biotechnol. Bioeng. 2010;105: 98–108. © 2009 Wiley Periodicals, Inc.     

Solid-state fermentation: a continuous process for fungal tannase production

Truly continuous solid-state fermentations with operating times of 2-3 weeks were conducted in a prototype bioreactor for the production of fungal (Penicillium glabrum) tannase from a tannin-containing model substrate. Substantial quantities of the enzyme were synthesized throughout the operating periods and (imperfect) steady-state conditions seemed to be achieved soon after start-up of the fermentations. This demonstrated for the first time the possibility of conducting solid-state fermentations in the continuous mode and with a constant noninoculated feed. The operating variables and fermentation conditions in the bioreactor were sufficiently well predicted for the basic reinoculation concept to succeed. However, an incomplete understanding of the microbial mechanisms, the experimental system, and their interaction indicated the need for more research in this novel area of solid-state fermentation.     

Solid-state fermentation: a promising microbial technology for secondary metabolite production

Solid state (substrate) fermentation (SSF) has been used successfully for the production of enzymes and secondary metabolites. These products are associated with the stationary phase of microbial growth and are produced on an industrial scale for use in agriculture and the treatment of disease. Many of these secondary metabolites are still produced by submerged liquid fermentations (SmF) even though production by this method has been shown to be less efficient than SSF. As large-scale production increases further, so do the costs and energy demands. SSF has been shown to produce a more stable product, requiring less energy, in smaller fermenters, with easier downstream processing measures. In this article we review an important area of biotechnology, since the recent evidence indicates that bacteria and fungi, growing under SSF conditions, are more than capable of supplying the growing global demand for secondary metabolites.     

固态混合发酵提高木聚糖酶和纤维素酶活力的研究

研究了接种比例、接种时间、碳源、氮源等因素对木霉和黑曲霉混合发酵产木聚糖酶和纤维素酶的影响。试验结果表明,当木霉和黑曲霉按4:6同时接种,以玉米芯3．75g、麸皮3．75g、葡萄糖37．5mg为混合碳源,Mandels营养盐11．5mL、添加NH_4NO_37．5mg为氮源,在84h产纤维素酶活力达到230IU/g干物质,木聚糖酶活力达到1308IU/g干物质,与两菌纯培养相比,纤维素酶活力提高163％,木聚糖酶活力提高79．5％。