Biohydrogen production by Clostridium butyricum and Rhodopseudomonas palustris in Co-cultures

This study evaluated biohydrogen production by co-culture of Clostridium butyricum and Rhodopseudomonas palustris. C. butyricum and R. palustris were grown separately and together as batch cultures. Hydrogen production, growth, NH₄-N, total volatile fatty acid production, and sucrose degradation were monitored. The hydrogen production of the co-culture produced 562 ml, R. palustris 426 ml, and C. butyricum 333 ml. The co-culture produced 2.16 mol H₂/mol sucrose, C. butyricum and R. palustris produced 1.77 and 1.64 mol H₂/mol sucrose, respectively. The co-culture was more efficient in the hydrogen production. Therefore, the co-culture is a good method for biohydrogen fermentation.     

Batch and continuous biosorption of Cu by immobilized biomass of Arthrobacter sp.

The ability of free and polysulphone immobilized biomass of Arthrobacter sp. to remove Cu²⁺ ions from aqueous solution was studied in batch and continuous systems. The Langmuir and Freundlich isotherm models were applied to the data. The Langmuir isotherm model was found to fit the sorption data indicating that sorption was monolayer and uptake capacity (Q^o) was 175.87 and 158.7 mg/g for free and immobilized biomass respectively at pH 5.0 and 30 °C temperature, which was also confirmed by a high correlation coefficient, a low RMSE and a low Chi-square value. A kinetic study was carried out with pseudo-first-order reaction and pseudo-second-order reaction equations and it was found that the Cu²⁺ uptake process followed the pseudo-second-order rate expression. The diffusivity of Cu²⁺ on immobilized beads increased (0.402 × 10⁻⁴ to 0.435 × 10⁻⁴ cm²/s) with increasing concentration from 50 to 150 mg/L. The maximum percentage Cu²⁺ removal (89.56%) and uptake (32.64 mg/g) were found at 3.5 mL/min and 20 cm bed height. In addition to this the Bed Depth Service Time (BDST) model was in good agreement with the experimental data with a high correlation coefficient (>0.995). Furthermore, sorption and desorption studies were also carried out which showed that polysulphone immobilized biomass could be reused for up to six sorption–desorption cycles.     

Possibility of converting indigenous Salvadora persica L. seed oil into biodiesel in Pakistan

In this research study, biodiesel has been successfully produced from vegetable seed oil of an indigenous plant Salvadora persica L. that meets the international biodiesel standard (ASTM D6751). The biodiesel yield was 1.57 g/5 g (31.4% by weight) and the in-situ transesterification ester content conversion was 97.7%. The produced biodiesel density was 0.894 g/mL, its kinematic viscosity 5.51 mm²/s, HHV 35.26 MJ/kg, flash point 210°C, cetane no. 61, and sulfur content 0.0844%. Thermal analysis of the biodiesel showed that 97% weight loss was achieved at 595°C with total oxidation of the biodiesel. The production energy efficiency was 0.46% with a lab scale setup, assuming the volume fraction ratio (volume of the sample/total volume of the equipment used). The results revealed that single-step in-situ transesterification method is suitable for the production of biodiesel from S. persica seed oil.     

Effects of the inhibitor of pyruvate dehydrogenase multi-enzyme complex on hydrogen production by fermentative microbes

The redox state of carbon sources directly affected the ratio of NADH/NAD⁺ which was coupled to the hydrogen production by Bacillus sp. FS2011. The addition of the inhibitor of pyruvate dehydrogenase multi-enzyme complex (PDHc)E1 could regulate hydrogen production by FS2011 or pretreated compost in batch cultivation. With the addition of appropriate amount of inhibitor, hydrogen production via the NADH pathway was increased, leading to the higher overall hydrogen production. The maximum hydrogen yields of 307.6 ± 13.21 mL/g by FS2011 with the inhibitor of 80 ppm and 362.1 ± 10.1 mL/g by pretreated compost with the inhibitor of 60 ppm were observed, which were increased by 8.7% and 17.8% compared with the controls, respectively. Meanwhile the production of soluble metabolic byproducts such as butyrate, acetate and so on were decreased, resulting in reducing the difficulty of wastewater treatment.     

Direct utilization of kitchen waste for bioethanol production by separate hydrolysis and fermentation (SHF) using locally isolated yeast

Kitchen wastes containing high amounts of carbohydrates have potential as low-cost substrates for fermentable sugar production. In this study, enzymatic saccharification of kitchen waste was carried out. Response surface methodology (RSM) was applied to optimize the enzymatic saccharification conditions of kitchen waste. This paper presents analysis of RSM in a predictive model of the combined effects of independent variables (pH, temperature, glucoamylase activity, kitchen waste loading, and hydrolysis time) as the most significant parameters for fermentable sugar production and degree of saccharification. A 100 mL of kitchen waste was hydrolyzed in 250 mL of shake flasks. Quadratic RSM predicted maximum fermentable sugar production of 62.79 g/L and degree of saccharification (59.90%) at the following optimal conditions: pH 5, temperature 60°C, glucoamylase activity of 85 U/mL, and utilized 60 g/L of kitchen waste as a substrate at 10 h hydrolysis time. The verification experiments successfully produced 62.71 ± 0.7 g/L of fermentable sugar with 54.93 ± 0.4% degree of saccharification within 10 h of incubation, indicating that the developed model was successfully used to predict fermentable sugar production at more than 90% accuracy. The sugars produced after hydrolysis of kitchen waste were mainly attributed to monosaccharide: glucose (80%) and fructose (20%). The fermentable sugars obtained were subsequently used as carbon source for bioethanol production by locally isolated yeasts: Saccharomyces cerevisiae, Candida parasilosis, and Lanchancea fermentati. The yeasts were successfully consumed as sugars hydrolysate, and produced the highest ethanol yield ranging from 0.45 to 0.5 g/g and productivity between 0.44 g L^–1 h^–1 and 0.47 g L^–1 h^–1 after 24-h incubation, which was equivalent to 82.06–98.19% of conversion based on theoretical yield.     

Removal of dicofol from water by immobilized cellulase and its reaction kinetics

Researches on the removal of dicofol catalyzed by immobilized cellulase were conducted. Factors, such as acidity, temperature, enzyme activity, and initial concentration of dicofol, which could influence the removal were studied. The optimal pH for dicofol removal by immobilized cellulase was approximately 4–7, broader than that for free enzymes. The removal efficiencies for immobilized and free cellulase both decreased with increasing initial concentration of dicofol. The K_m for immobilized cellulase was slightly lower than that of free cellulase, suggesting that substrate affinity may be enhanced by immobilization. The optimum temperatures for immobilized and free cellulase were 45 °C and 50 °C. The removal reaction for immobilized cellulase was found to be a first-order reaction. The activation energy was 64.3 kJ mol⁻¹. The continuous oxidation of dicofol carried out in the static system of immobilized cellulase showed that the removal efficiency of immobilized cellulase remained after six cycles of operation. Thus, the catalytic efficiency of cellulase was improved greatly. As evidenced by infrared and gas chromatography–mass spectrometry data, the mechanism of reaction might involve an attack by the OH free radical of cellulase at a weak location of the dicofol molecule, resulting in the removal of three chlorine atoms from dicofol, thus oxygenizing dicofol and producing 4,4′-dichloro-dibenzophenone.     

Batch sorption dynamics and equilibrium for the removal of lead ions from aqueous phase using activated carbon developed from coffee residue activated with zinc chloride

Lignocellulosic materials are good precursors for the production of activated carbon. In this work, coffee residue has been used as raw material in the preparation of powder activated carbon by the method of chemical activation with zinc chloride for the sorption of Pb(II) from dilute aqueous solutions.The influence of impregnation ratio (ZnCl₂/coffee residue) on the physical and chemical properties of the prepared carbons was studied in order to optimize this parameter. The optimum experimental condition for preparing predominantly microporous activated carbons with high pore surface area (890 m²/g) and micropore volume (0.772 cm³/g) is an impregnation ratio of 100%. The developed activated carbon shows substantial capability to sorb lead(II) ions from aqueous solutions and for relative impregnation ratios of 75 and 100%, the maximum uptake is practically the same. Thus, 75% represents the optimal impregnation ratio.Batch experiments were conducted to study the effects of the main parameters such as contact time, initial concentration of Pb(II), solution pH, ionic strength and temperature. The maximum uptake of lead(II) at 25 °C was about 63 mg/g of adsorbent at pH 5.8, initial Pb(II) concentration of 10 mg/L, agitation speed of 200 rpm and ionic strength of 0.005 M. The kinetic data were fitted to the models of pseudo-first order and pseudo-second order, and follow closely the pseudo-second order model. Equilibrium sorption isotherms of Pb(II) were analyzed by the Langmuir, Freundlich and Temkin isotherm models. The Freundlich model gives a better fit than the others.Results from this study suggest that activated carbon produced from coffee residue is an effective adsorbent for the removal of lead from aqueous solutions and that ZnCl₂ is a suitable activating agent for the preparation of high-porosity carbons.     

Phenol degradation using combined effects of hydrodynamic cavitation and oxidant: Doehlert matrix

Hydrodynamic cavitation (HC)-based treatments have been proposed for the degradation of phenol as a toxic pollutant. The present work aimed to optimize the degradation of phenol using HC by means of Doehlert experimental design, which has not been previously addressed. Initially, operational parameters of hydraulic characteristics of the pump, inlet pressure, solution pH, and initial concentration were optimized; later, the effects of pH solution and H₂O₂ loading or initial pollutant concentration on phenol degradation were explored using the Doehlert experimental design. It was observed that phenol degradation is strongly dependent on the pH of the solution. Also, the acidic condition favors the formation of hydroxyl radicals and thus, the degradation of phenol. Based on the Doehlert matrix, the 94.1% phenol degradation and 68.60% total organic carbon (TOC) were obtained in 180 min at 304.5 mg/L of hydrogen peroxide at an initial concentration of 20 mg/L, 2.0 pH, and 90 psi inlet pressure, providing a cavitational yield of 6.33 × 10⁻⁶ mg/J and minimum treatment cost of US$/L 0.13. Overall, it has been observed that HC can be a promising route for the removal of pollutants (phenol) effectively using hydrogen peroxide as an additive.     

Removal of copper from aqueous solution by Ascophyllum nodosum immobilised in hydrophilic polyurethane foam

The seaweed Ascophyllum nodosum was pre-treated by successive washes in distilled water and dilute acid, dried, and pulverised to produce particles of <150 microm. These were immobilised during the manufacturing process of Hypol 2002 polymer to form a biomass/polymer matrix that was stable and easy to handle. In making the composite a mixing speed of 360 rpm for 20-30 s with 2% (w/w) addition of surfactant to pre-polymer was found to be ideal. The average pore sizes for different water polymer mixes (expressed as volume ratios) were 1.66 mm +/- 0.98 (ratio 0.75:1), 1.58 mm +/- 0.76 (ratio 1:1), 1.64 mm +/- 0.6 (ratio 1.5:1) and 1.11 mm +/- 0.615 (ratio 2:1). The biomass/polymer was used alongside free native biomass in an initial adsorption experiment using a 0.0315 mmol dm(-3) Cu (II) solution and gave a copper uptake capacity [Formula: see text] of 0.037 mmol Cu g(-1) dry weight seaweed in both cases which represented approximately 85% of total initially available copper. In later adsorption isotherm experiments using Cu concentrations between 0.0315 and 0.944 mmol dm(-3) at pH 5.0 and immobilized biomass over five consecutive adsorption/desorption cycles the biomass/polymer showed an initial lowering of adsorption capacity but stabilised at 0.23 mmol g(-1) dry weight by the third re-use. The q(max) of the immobilised biomass decreased from 0.55 and 0.416 mmol of Cu g(-1) dry weight when pH was lowered from 4.0 to 3.0, and increased from 0.576 mmol g(-1) dry weight (biomass) at 283 K to 0.636 mmol g(-1)(biomass) at 303 K.     

Comparison of different pre-treatment methods for enriching hydrogen-producing bacteria from intertidal sludge

Batch tests of cultivations were conducted to analyze influences of pre-treatment methods (heat–shock, acid, and alkaline) on hydrogen production. The hydrogen yields of the pre-treated samples were significantly higher than those without pre-treatment. Heat–shock pre-treatment yielded maximum hydrogen (75.5 ± 4.0 mL/g sucrose_removed), and had the highest sucrose removal efficiency (81.20 ± 1.23%). Heat–shock pre-treatment produced more ethanol and acetate (80.44 ± 0.55% of the total soluble metabolites), which belonged to ethanol-type fermentation. Denaturing gradient gel electrophoresis (DGGE) profiles showed that pre-treatment methods affected the composition of microbial communities. The results showed that pre-treatment methods play a key role in the hydrogen production process of marine hydrogen-producing microflora.     

冻干壳聚糖微球固定化纤维素酶的研究

分别以冻干壳聚糖微球和湿壳聚糖微球为载体,戊二醛为交联剂进行纤维素酶的固定化研究,并对2种固定化酶的热稳定性、米氏常数、重复利用次数、pH值加以对比分析。确定酶固定化的适宜条件为：0．03g冻干壳聚糖微球与10mL4g/L戊二醛交联4h后,加入10mg酶固定2h,酶活力回收率为96．3％;0．1g湿壳聚糖微球与10mL 2g／L戊二醛交联2h后,加入6mg酶固定4h,酶活力回收率为62．4％。与游离酶相比,2种固定化酶的米氏常数均降低;具有很好的热稳定性;最适酶解温度分别为60℃,50℃;酶解反应适宜pH范围3．0—4．0,最适pH值均向酸性方向移动。冻干载体更易与酶分子结合,酶活力回收率高于湿载体固定化酶。     

Biomass from phytopathogens and culture conditions improve Penicillium chrysogenum antimicrobial activity and antifungal compounds production

The present study evaluated the effect of culture conditions and phytopathogenic strain co-culture on the production of antimicrobial metabolites and antifungal activity of Penicillium chrysogenum R1, which PCR identified. Antimicrobial activity was determined using the Hunter-Hunter experimental design with three factors (pH, incubation temperature, and inoculum, at two levels each). The antifungal metabolites, β 1-3 glucanase and chitinase, produced in the presence of live and inactivated Fusarium oxysporum Fsox C11 biomass, were evaluated using HPLC-MS and GC-MS. Results showed that P. chrysogenum inhibited the growth of five phytopathogenic fungal strains, and the most significant inhibition was observed for F. oxysporum Fsox C11. The best conditions to achieve the highest antifungal activity of the cell-free extract were pH 7, 28°C, 1 × 10⁶ spores/mL, and 144 h of fermentation, observing 86% inhibition of F. oxysporum Fsox C11 growth. Production of antifungal metabolites such as 1,4-benzoquinone imine, viridicatic acid, phenol-5-methyl-2-(1-methyl ethyl), and hydrolytic enzymes β 1-3 glucanase and chitinase was detected. The results define the perspective in designing new processes and products for biocontrol phytopathogens.     

The Effects of Gas Flow Rate and the Interval Time of Water Supplement on Ethanol Production of Rice Straw by Simultaneous Saccharification and Fermentation

In the present work, characteristics of ethanol production from a single particle composing of pretreated rice straw, cellulase, and β-glucosidase were invesitgated by simultaneous saccharification and fermentation (SSF). The experiment experienced a start-up stage for S. cerevisiae biofilm formation, which was operated at an initial pH value of 4.8 for yeast solution, culture temperature of 30°C, flow rate of 0.8 mL/min for yeast solution, and stably operating stage for ethanol production at a culture temperature of 30°C. Investigations found that the maximal ethanol yield of 9.7 mg/g and the biofilm thickness of 0.37 mm were obtained at 30 mL/min of carrier gas flow rate. Also, the optimal interval time of water supplement was 4 h for SSF. The results show that the appropriate gas flow rate and the interval time of water supplement can keep the high activities of biofilm and enzymes during SSF and result in a high ethanol yield.     

Characteristics of Anaerobic Fermentation with Different Parts of Corn Stalks at Low Concentrations

In order to obtain the characteristics of anaerobic fermentation with different parts of corn stalks at low concentrations, air-dried corn stalks stem bark (SB), stem pith (SP), leaves (L), and corn stalks (CS) were, respectively, mixed with cow dung to perform fermentation at the temperature of 35 ^oC and carbon-to-nitrogen ratio (C/N) of 25. Mixed with cow dung compost, the fermentation broths were adjusted to a neutral pH value. Along with the enhancing of the total solid (TS) content of SB, SP, L, and CS fermentation broths, both of the daily biogas yields and methane contents increased under the same fermentation condition, except for Sample TS 6% of L. The optimal TS content of SB, SP, L, and CS broth is 8%, 5%, 10%, and 8%, separately. In 35 days, the highest methane yield of SB, SP, L, and CS broth was 125.0 mL/(volatile solid) VS g, 115.3 mL/VS g, 109.7 mL/VS g, and 80.0 mL/VS g, respectively, and the potential of methane transformation production of broth ranks as: SB> L> SP> CS. Daily methane producing rate of SB, SP, and L broth are faster than that of CS. It is necessary to separate the corn stalks into different parts to ferment because the optimal fermentation concentrations for the different parts are different. Additionally, the Gompertz equation was also adopted to simulate the anaerobic digestion process of different materials. The Gompertz equation fitting parameters show that the biodegradation (from easy to difficult) was: L < SP < SB < CS.     

固定化真菌漆酶对分散兰-2BLN的脱色和降解

采用改良壳聚糖固定化的真菌漆酶对染料分散兰-2BLN进行脱色和降解条件的研究,探索了固定化漆酶活力、处理时间、染料浓度、温度和pH对其降解效果的影响。结果表明,固定化漆酶脱色降解分散兰-2BLN的适宜条件为：固定化漆酶活力18.2U／mL,染料浓度100mg／L,温度40℃,pH4.6,在上述条件下降解1.5h,分散兰-2BLN脱色率能达到87.68％。重复分批使用固定化漆酶处理2BLN兰,在使用6批次后,脱色率仍能保持在55％以上,其催化效率得到了较大提高。     

Benthic Algal (Periphyton) Growth Rates in Response to Nitrogen and Phosphorus: Parameter Estimation for Water Quality Models

Nitrogen (N) and phosphorus (P) are significant pollutants that can stimulate nuisance blooms of algae. Water quality models (e.g., Water Quality Simulation Program, CE‐QUAL‐R1, CE‐QUAL‐ICM, QUAL2k) are valuable and widely used management tools for algal accrual due to excess nutrients in the presence of other limiting factors. These models utilize the Monod and Droop equations to associate algal growth rate with dissolved nutrient concentration and intracellular nutrient content. Having accurate parameter values is essential to model performance; however, published values for model parameterization are limited, particularly for benthic (periphyton) algae. We conducted a 10‐day mesocosm experiment and measured diatom‐dominated periphyton biomass accrual through time as chlorophyll a (chl a) and ash‐free dry mass (AFDM) in response to additions of N (range 5–11,995 µg nitrate as nitrogen [NO₃‐N]/L) and P (range 0.89–59.51 µg soluble reactive phosphorus/L). Resulting half‐saturation coefficients and growth rates are similar to other published values, but minimum nutrient quotas are higher than those previously reported. Saturation concentration for N ranged from 150 to 2,450 µg NO₃‐N/L based on chl a and from 8.5 to 60 µg NO₃‐N/L when based on AFDM. Similarly, the saturation concentration for P ranged from 12 to 29 µg‐P/L based on chl a, and from 2.5 to 6.1 µg‐P/L based on AFDM. These saturation concentrations provide an upper limit for streams where diatom growth can be expected to respond to nutrient levels and a benchmark for reducing nutrient concentrations to a point where benthic algal growth will be limited.     

Enzymatic hydrolysis of banana stems (Musa acuminata): Optimization of process parameters and inhibition characterization

In current work, an optimum solid loading (solid: liquid = 1:20), pH (4.8), temperature (50°C), and enzyme dosing of 20 filter paper unit (amount of enzyme required to release 1 µmol of glucose as reducing sugar from filter paper in per mL per minute) were enumerated for enzymatic hydrolysis of banana stem using cellulase from Trichoderma reesei. Further, inhibition study on enzymatic hydrolysis of banana stem was investigated by the supplementation of monosaccharides (glucose, galactose, mannose, xylose, and arabinose), disaccharide (cellobiose), and inhibitors (acetic acid and furfural obtained from pre-enzymatic hydrolysis steps). Glucose and cellobiose showed inhibitory effect on enzymatic hydrolysis of pretreated banana stem at or above 8 g/L while galactose, mannose, and xylose showed a significant inhibitory effect at or above 4 g/L. Instead of inhibition, arabinose enhanced the enzymatic hydrolysis with increase in total reducing sugars. Acetic acid did not show any significant inhibition while furfural inhibited the system at a comparative low concentration of 2 g/L. Further, scanning electron microscopy analysis was performed to investigate the difference in ultra-structural morphology of raw biomass, pretreated biomass, and biomass obtained after enzymatic hydrolysis.     

Arsenic and chromium removal by mixed magnetite–maghemite nanoparticles and the effect of phosphate on removal

Adsorption of arsenic and chromium by mixed magnetite and maghemite nanoparticles from aqueous solution is a promising technology. In the present batch experimental study, a commercially grade nano-size ‘magnetite’, later identified in laboratory characterization to be mixed magnetite–maghemite nanoparticles, was used in the uptake of arsenic and chromium from different water samples. The intent was to identify or develop a practical method for future groundwater remediation. The results of the study showed 96–99% arsenic and chromium uptake under controlled pH conditions. The maximum arsenic adsorption occurred at pH 2 with values of 3.69 mg/g for arsenic(III) and 3.71 mg/g for arsenic(V) when the initial concentration was kept at 1.5 mg/L for both arsenic species, while chromium(VI) concentration was 2.4 mg/g at pH 2 with an initial chromium(VI) concentration of 1 mg/L. Thus magnetite–maghemite nanoparticles can readily adsorb arsenic and chromium in an acidic pH range. Redox potential and pH data helped to infer possible dominating species and oxidation states of arsenic and chromium in solution. The results also showed the limitation of arsenic and chromium uptake by the nano-size magnetite–maghemite mixture in the presence of a competing anion such as phosphate. At a fixed adsorbent concentration of 0.4 g/L, arsenic and chromium uptake decreased with increasing phosphate concentration. Nano-size magnetite–maghemite mixed particles adsorbed less than 50% arsenic from synthetic water containing more than 3 mg/L phosphate and 1.2 mg/L of initial arsenic concentration, and less than 50% chromium from synthetic water containing more than 5 mg/L phosphate and 1.0 mg/L of chromium(VI). In natural groundwater containing more than 5 mg/L phosphate and 1.13 mg/L of arsenic, less than 60% arsenic uptake was achieved. In this case, it is anticipated that an optimum design with magnetite–maghemite nanoparticles may achieve high arsenic uptake in field applications.     

Effect of Fenton pretreatment on anaerobic digestion of olive mill wastewater and olive mill solid waste in mesophilic conditions

The olive mill waste (OMW) generated from olive oil extraction process constitutes a major environmental concern owing to its high organic and mineral matters and acidic pH. Anaerobic digestion (AD) is a main treatment for reducing the organic matter and toxic substances contained in OMW and generating at the same time, energy in the form of biogas. AD of OMW that contains lignocellulose is limited by the rate of hydrolysis due to their recalcitrant structure. This study is devoted to the effect of Fenton process (FP) pretreatment on olive mill wastewater (OMSW) /olive mill solid waste (OMWW) co-digestion to improve their digestibility and in this way the biogas production. The FP pretreatment was performed in batch mode at 25°C, various H₂O₂/[Fe²⁺] ratios (100–1200), catalyst concentration ([Fe²⁺]) ranging from 0.25 to 2 mM, reaction time varying from 30 to150 min, and different pH (3–11). The best performance was obtained with H₂O₂/[Fe²⁺] = 1000, [Fe²⁺] = 1.5 mM, 120 min, and pH 3. Biochemical methane potential (BMP) tests conducted in batch wise digester and at mesophilic conditions (37 °C) showed that cumulative biogas and methane production were higher without FP treatment, and correspond to 699 and 416 mL/g VS, respectively. However, pre-treated OMSW results into an increase of 24% of methane yield. After 30 days of AD, the methane yield was 63%, 54%, and 48%, respectively, for OMSW treated without iron precipitation, with iron precipitation and untreated OMSW sample.     

城市生活垃圾中可生化单基质的厌氧消化

在厌氧消化系统中,发酵细菌最主要的利用基质是淀粉、纤维素、脂肪和蛋白质等。本试验分别选取米饭、黄豆、芹菜和肥肉为上述四种基质的代表物质,通过对各物质进行的厌氧消化试验,探讨了它们的厌氧消化性能。结果表明。米饭在发酵初期降解速率最快,酸化也最明显。同时将消化初始阶段的pH控制在6．5时能使消化进入产甲烷阶段,没控制的只能停留在水解产酸阶段。将黄豆厌氧消化初期的pH控制在6．5并不能使消化顺利进行。将芹菜厌氧消化的初始pH值控制在6．5时可以加快它的降解速率。肥肉的厌氧消化也只有在对其消化进程控制pH值时才能顺利被降解。同时肥肉在厌氧消化进程中表现出了高产甲烷性能,产甲烷阶段累积产气量达13758mL,占总产气量的93．59％．