Inhibitory Effect Of Phenol Research Articles

Enhancement of phenol biodegradation: Metabolic division of labor in co-culture of Stenotrophomonas sp. N5 and Advenella sp. B9

The aim of this work is to study the synergistic effect of Stenotrophomonas sp. N5 and Advenella sp. B9 co-culture (COC) on enhancement of phenol biodegradation. These two strains utilizing phenol as sole carbon and energy source were isolated from phenol-containing coking wastewater. The results of biodegradation experiment showed the COC of N5 and B9 has stronger capability to degrade phenol than either of mono-culture (MOC). Growth kinetics studies indicated inhibitory effect of phenol on COC was reduced by the interaction of N5 and B9 in COC. The RNA-Seq results demonstrated that phenol biodegradation was enhanced by metabolic division of labor (DOL) in COC based on the expression of key genes for phenol degradation. GO enrichment analysis of differentially expressed genes (DEGs) indicated DEGs between COC and MOC degradation systems are mainly concentrated in the synthesis of cell components, microbial growth and metabolism, and catalytic activity. The expression of 3 transcriptional factors (LysR, Two-component system response regulator, and TetR families) which can regulate degradation of aromatic compounds, was identified beneficial to phenol degradation.

Soil Bioaugmentation with Pseudomonas aeruginosa S-CSR-0013 Eliminates the Inhibitory Effect of Phenol on Germination of Chickpea (Cicer arietinum) Seeds

Phenol is one of the 50 bulkiest chemicals produced in the world and is one of the priority pollutants found in various industrial effluents at varying levels. Its toxicity to fauna and flora has been well established. However, information on its effect on germination of crop seeds is scanty. In this study the effects of phenol on germination of 11 different crop seeds were tested by filter paper as well as soil methods. Chickpea, mung bean, and long-podded cowpea seeds were found to be highly sensitive with drastic reduction in germination percentage (GP) and seedling vigour (SV) in the presence of phenol even at very low concentrations, chickpea being most vulnerable. Marked decrease in protease and amylase activities in germinating seeds was also observed. Seed viability was inversely proportional to the concentration of phenol. The inhibitory effect of phenol on germination was eliminated effectively by bioaugmentation of the soil with <i>Pseudomonas aeruginosa</i> S-CSR-0013. Pre-inoculation of the soil eight days before sowing the seeds exhibited complete protection of GP and SV. The bacterium degraded phenol efficiently from the soil with concomitant growth. It can be concluded that phenol-contaminated soils could be effectively bioremediated to enable normal seed germination and seedling growth.<div><br></div>

Understanding the structural characteristics of water-soluble phenolic compounds from four pretreatments of corn stover and their inhibitory effects on enzymatic hydrolysis and fermentation

BackgroundFor bioethanol production from lignocellulosic biomass, phenolics derived from pretreatment have been generally considered as highly inhibitory towards enzymatic hydrolysis and fermentation. As phenolics are produced from lignin degradation during pretreatment, it is likely that the pretreatment will exert a strong impact on the structure of phenolics, resulting in varied levels of inhibition of the bioconversion process. Despite the extensive studies on pretreatment, it remains unclear how pretreatment process affects the properties of generated phenolics and how the inhibitory effect of phenolics from different pretreatment varies on enzymatic hydrolysis and fermentation.ResultsIn this study, the structural properties of phenolic compounds derived from four typical pretreatment [dilute acid (DA), liquid hot water pretreatment (LHW), ammonia fiber expansion (AFEX) and alkaline pretreatment (AL)] were characterized, and their effect on both enzymatic hydrolysis and fermentation were evaluated. The inhibitory effect of phenolics on enzymatic hydrolysis followed the order: AFEX > LHW > DA > AL, while the inhibitory effect of phenolics on Zymomonas mobilis 8b strain fermentation followed the order: AL > LHW > DA > AFEX. Interestingly, this study revealed that phenolics derived from AFEX showed more severe inhibitory effect on enzymatic hydrolysis than those from the other pretreatments at the same phenolics concentrations (note: AFEX produced much less amount of phenolics compared to AL and DA), while they exhibited the lowest inhibitory effect on fermentation. The composition of phenolics from different pretreatments was analyzed and model phenolics were applied to explore the reason for this difference. The results suggested that the amide group in phenolics might account for this difference.ConclusionsPretreatment process greatly affects the properties of generated phenolics and the inhibitory effects of phenolics on enzymatic hydrolysis and fermentation. This study provides new insight for further pretreatment modification and hydrolysate detoxification to minimize phenolics-caused inhibition and enhance the efficiency of enzymatic hydrolysis and fermentation.

Inhibitory Effect of Phenol on Phosphorus Removal Performance of an EBPR System

An SBR reactor was operated to study the inhibitory effect of different concentrations of phenol (5, 10, 30, 50, 100, 150, and 200 mg·L-1) on the phosphorus removal performance of an EBPR system. The results showed that when the phenol concentration was no higher than 50 mg·L-1, the removal efficiencies of COD and PO43--P were above 85%. The system showed efficient pollutant removal performance. However, when phenol was higher than 100 mg·L-1, phosphorus removal performance of the reactor decreased drastically. When phenol concentration was 200 mg·L-1, the system lost phosphorus removal performance after only 22 cycles. The average COD removal efficiency dropped to 61.3%, and high removal performance recovery was not observed in the short term. Meanwhile, it was found that long-term dosing of phenol inhibited phosphorus removal of the sludge subjected to EBPR. Furthermore, the inhibition on aerobic phosphate uptake was greater than that on anaerobic phosphate release. In addition, the limited sludge bulking disappeared gradually owing to acclimation of the sludge to toxicity with a low phenol concentration (≤ 50 mg·L-1). However, high concentration of phenol induced sludge bulking was difficult to recover. The short-term impact experiments showed that effluent COD and phosphorus fluctuation caused by phenol could be recovered gradually by removing phenol, suggesting that the inhibitory effect of phenol on phosphorus removal was reversible.

The Role of Dietary Phenolic Compounds in Protein Digestion and Processing Technologies to Improve Their Antinutritive Properties.

Digestion is the key step for delivering nutrients and bioactive substances to the body. The way different food components interact with each other and with digestive enzymes can modify the digestion process and affect human health. Understanding how food components interact during digestion is essential for the rational design of functional food products. Plant polyphenols have gained much attention for the bioactive roles they play in the human body. However, their strong beneficial effects on human health have also been associated with a negative impact on the digestion process. Due to the generally low absorption of phenolic compounds after food intake, most of the consumed polyphenols remain in the gastrointestinal tract, where they then can exert inhibitory effects on enzymes involved in the degradation of saccharides, lipids, and proteins. While the inhibitory effects of phenolics on the digestion of energy-rich food components (saccharides and lipids) may be regarded as beneficial, primarily in weight-control diets, their inhibitory effects on the digestion of proteins are not desirable for the reason of reduced utilization of amino acids. The effect of polyphenols on protein digestion is reviewed in this article, with an emphasis on food processing methods to improve the antinutritive properties of polyphenols.

Simulation of phenol biodegradation by Ralstonia eutropha in a packed-bed bioreactor with batch recycle mode using CFD technique

Packed-bed reactors are widely used in biological treatment processes. The complete simulation of the reactions and concentration profiles of the reactors, which are necessary for a successful reactor design, operation, and scale-up, are now possible due to extensive improvements of numerical methods and computational power. In the present work, phenol biodegradation was studied in a packed-bed bioreactor operating in the recycling batch mode using the computational fluid dynamics (CFD) method. A transient comprehensive 3D CFD was developed to simulate the dynamic behavior of batch phenol biodegradation by Ralstonia eutropha in a Kissiris-immobilized cell bioreactor. The model combined the porous medium CFD model with two kinetic equations, namely the Haldane and Luong inhibition models, to consider the inhibitory effect of phenol at high concentrations. The simulation results of the phenol concentration variation in different initial phenol concentrations (2.13, 4.26, 6.39, and 8.52mol/m3) and recirculation flow rates (10, 25, and 40ml/min) were validated against experimental data. Despite the assumptions, the simulation results create an acceptable assurance of the simulation precision with good agreement with experimental data.

Inhibitory Effects of Phenolics and Saponins From Commonly Consumed Food Legumes in China Against Digestive Enzymes Pancreatic Lipase and α-Glycosidase

Total phenolic and saponin components were extracted from 13 commonly consumed food legumes produced in China, and then a systematic comparative study was conducted to investigate their inhibitory effects against digestive enzymes, pancreatic lipase, and α-glycosidase, respectively. Saponin extract (1 mg/mL) from black bean exhibited the highest (41.8%) pancreatic lipase inhibitory effect, followed by phenolic extract from adzuki bean with 36.3%, saponin extract from yellow soybean with 34.1%, saponin extract from pinto bean with 32.6%. It is worth mentioning that both phenolic and saponin extracts from the mung bean, adzuki bean, lima bean, and pinto bean exhibited inhibitory effects against pancreatic lipase. Among four beans, the adzuki bean had the highest inhibitory effects against pancreatic lipase activity. In the α-glycosidase assays, phenolic extracts exhibited stronger α-glycosidase inhibitory activity than that of saponins in general. Phenolic extracts of the adzuki bean, black bean, fava bean, lentil, rock bean, and red kidney bean inhibited over 80% of α-glycosidase activity at the concentration of 1 mg/mL. Both phenolic and saponin extracts from the adzuki bean and rock bean exhibited inhibitory effects against α-glycosidase. The results indicate that adzuki bean is one of the best target beans for further study on their anti-obesity and anti-diabetes effects via cell and animal models.

Biodegradation of phenol from saline wastewater using forward osmotic hollow fiber membrane bioreactor coupled chemostat

A chemostat was coupled with a forward osmotic hollow fiber membrane bioreactor (FOHFMB) for treatment of high strength saline phenolic wastewater using Pseudomonas putida ATCC 11,172. The microorganisms were protected from the inhibitory effects of phenol and sodium chloride through dilution of the feed wastewater. This resulted in high cell growth and biodegradation rates during transient operation and steady state was achieved within 20h. Effluent from the chemostat was desalinated in the FOHFMB through forward osmosis (FO) using magnesium chloride as the draw solute (DS). Permeate flux during FO remained stable for over 70h in the orientation with DS facing the porous side of the membranes (PRO mode of operation). Water used for dilution could be recovered using 0.8M DS when the wastewater did not contain any sodium chloride, whereas, 1.5M DS was required to recover water from the wastewater containing 0.6M sodium chloride. Biomass attachment on the membranes during FO operation was visualized using SEM, which showed that FO membranes was susceptible to fouling propensity and biomass deposition on the membranes was directly associated with permeate flux. Nevertheless, biofouling of membranes was reversible and membrane performance was recovered by osmotic backwashing.

Inhibitory effects of phenolic compounds from Artocarpus styracifolius on respiratory burst of rat neutrophils

Context: Searching for polymorphonuclear neutrophils (PMNs) respiratory burst inhibitors is an important topic in the treatment of human diseases associated with inflammation.Objective: To investigate the inhibitory effects of phenolics isolated from Artocarpus styracifolius Pierre (Moraceae) on respiratory burst induced by phorbol myristate acetate (PMA).Materials and methods: The anti-respiratory burst activities of eight phenolics (20 µM) were assessed by determining luminol-dependent chemiluminiscence in rat PMNs. Cytotoxicity of active compounds (1–1000 µM) was assayed by Trypan blue dye exclusion method. Cell-free models were employed to evaluate scavenging capacity of active compounds (20 µM) against reactive oxygen species.Results: The PMA-induced respiratory burst was significantly inhibited (p < 0.05) by six isoprenylated phenolics (AS1–6) at the concentration of 20 µM (below the toxic concentration) with the inhibition rate ranging from 25.0 to 99.6%. The inhibitory potency estimated by IC50 was in the order of AS1 (3.1 µM) >AS6 (5.9 µM) >AS2 (9.1 µM) >AS3 (10.0 µM) >AS5 (29.7 µM) >AS4 (57.7 µM). AS1–4, four isoprenylated flavones, potently quenched superoxide anion, hydroxyl radical, and hydrogen peroxide at the concentration of 20 µM with their scavenging rates in the range of 30.1–78.1%, 35.4–69.7%, and 65.5–86.3%, respectively. In contrast, AS5–6, two isoprenylated 2-arylbenzofurans, showed less effect than that exhibited by AS1–4.Conclusion and discussion: The isoprenylated phenolics from A. styracifolius can potently inhibit PMA-induced respiratory burst in rat neutrophils without showing cytotoxicity. The inhibitory effects of these isoprenylated phenolics on the respiratory burst might depend on their different types of structure.

Revealing phenol tolerance of indigenous phenol degraders isolated from Northeast Taiwan

This novel attempt used chemostat pulse technique (CPT) and transient dynamics of dissolved oxygen (DO) in CSTR to quantify stimulating or inhibitory effects of phenol upon indigenous isolates for phenol degradation/tolerance. As known, phenol tolerance and degradation of isolates strongly depend upon phenol toxicity and their associated biodegradability to phenol. Although phenol at higher levels (e.g., 2000 mg/L) was toxic, lower level phenol (e.g., 200 mg/L) still exhibited stimulating effects to growth of isolated bacteria. Our findings also showed that time courses of dissolved oxygen (DO) of repetitive pulse injection tests might disclose the characteristics of species evolution in mixed consortia. Compared to Cupriavidus taiwanensis, higher tolerance of isolated strains (i.e., Klebsiella sp. and Lysinibacillus sp.) suggested why they had promising capability for phenol degradation. This study can help uncover not only the mysteries of phenol tolerance, but also species evolution in mixed consortia for system analysis in wastewater treatment.

Phenolic Control of Plant Nitrogen Acquisition through the Inhibition of Soil Microbial Decomposition Processes: A Plant-Microbe Competition Model

Phenolics are a dominant class of plant secondary metabolites that have strong effects on various ecosystem processes. The ecological significance of these compounds, however, is still poorly understood. We hypothesized that the inhibitory effects of phenolics on microbial activity could enhance plant nitrogen acquisition by relaxing competition between plants and microbes. To test this hypothesis theoretically, we constructed a novel and simple mechanistic model by unifying two concepts: one is a new paradigm of nitrogen cycling which considers the uptake of organic nitrogen by plants, and the other is that phenolics can regulate nitrogen cycling by inhibiting microbial decomposition processes. Our plant-microbe competition model consists of five compartments (plants, soil microbes, debris, organic nitrogen and inorganic nitrogen) and incorporates the essential processes of nitrogen cycling: plant uptake of monomers, competition between plants and microbes, and the depolymerization process. Our analysis showed that plant nitrogen acquisition was maximized at intermediate levels of phenolics, but only when plants could utilize organic nitrogen. Furthermore, this pattern occurred over a broad range of parameter conditions. Our study successfully demonstrated the potential role of phenolics in plant nitrogen acquisition throughout natural environments.

APPLICATION OF AEROBIC RESPIROMETRY: STUDIES ON THE IMPACT OF HUMATE ON BIOLOGICAL TREATMENT OF MUNICIPAL SEWAGE

This paper describes an application of aerobic respirometry to investigate the influence of humic matter (humate) on biological processes in dilution water and in municipal sewage. Standard product PolySeed, a consortium of bacteria considered to be representative of those found in an activated sludge, was used as a source of biomass. The results indicate that aerobic respirometry is a simple and convenient method for studies of biological processes. It was observed that an addition of humate at doses up to 2000 mg l−1 stimulated biological processes both in dilution water and in sewage. Also, it was found that humate is effective in suppressing an inhibitory effect of phenol and copper on the biomass. The results of the studies suggest than the application of humate has great potential in wastewater treatment, as it can serve as a source of additives, stimulating biological activity and removing toxic inhibitors of biological processes.

Kinetics of phenol and m-cresol biodegradation by an indigenous mixed microbial culture isolated from a sewage treatment plant

An acclimatized mixed microbial culture, predominantly Pseudomonas sp., was enriched from a sewage treatment plant, and its potential to simultaneously degrade mixtures of phenol and m-cresol was investigated during its growth in batch shake flasks. A 2(2) full factorial design with the two substrates at two different levels and different initial concentration ranges (low and high), was employed to carry out the biodegradation experiments. The substrates phenol and m-cresol were completely utilized within 21 h when present at low concentrations of 100 mg/L for each, and at high concentration of 600 mg/L for each, a maximum time of 187 h was observed for their removal. The biodegradation results also showed that the presence of phenol in low concentration range (100-300 mg/L) did not inhibit m-cresol biodegradation. Whereas the presence of m-cresol inhibited phenol biodegradation by the culture. Moreover, irrespective of the concentrations used, phenol was degraded preferentially and earlier than m-cresol. A sum kinetics model was used to describe the variation in the substrate specific degradation rates, which gave a high coefficient of determination value (R2 > 0.98) at the low concentration range of the substrates. From the estimated interaction parameter values obtained from this model, the inhibitory effect of phenol on m-cresol degradation by the culture was found to be more pronounced compared to that of m-cresol on phenol. This study showed a good potential of the indigenous mixed culture in degrading mixed substrate of phenolics.

KINETICS OF PHENOL AND BENZOATE BIODEGRADATION IN STATIC CULTIVATION SYSTEM BY Burkholderia cepacia G4.

Kinetics of phenol and benzoate degradation by Burkholderia cepacia G4 in classical batch mode of static culture were investigated over a wide range of initial substrate concentrations applied as single substrates. Due to better adaptation to changing conditions, faster degradation of both phenol and benzoate was observed when higher concentrations were used. The results show decrease of the biomass yield coefficient, YX/S, from 0.83 to 0.31 g g-1 when the initial phenol concentration was increased from 0.54 to 0.73 g L-1, supporting the well known inhibitory effect of phenol. On the other hand, linear increasing of the yield coefficient was observed with increasing benzoate concentration. During all experiments, maximum specific substrate consumption rates, rSmax, were reached to 0.27 g g-1h-1 for phenol and to 0.40 g g-1h-1 when benzoate was the sole source of carbon in the bioreactor. In the present study, minor inhibitory effect of benzoate was observed during their investigated concentration range. To explain their degradation modelling, experimental data of both phenol and benzoate biodegradation were fitted using various kinetic models. The results demonstrated that the Yano and Koga equation gave the best fit, compared with the other models. It means that biodegradation of phenol and benzoate can be described by the same kinetic model. Based on the kinetic data, all experiments were not sensitive to change in the saturation constant, KS; therefore, KS-value was fixed at 0.042 and 0.068 g L-1 for phenol and benzoate, respectively. After that, rSmax and the inhibition constant, Ki, parameters were re-fitted in all experiments. In general, the kinetic parameters of both phenol and benzoate degradation were influenced by the initial substrate and bacterial cell mass concentrations, in addition to adaptation with changing in the culture conditions.

Biodegradation of Phenol by Acclimatized Pseudomonas putida Cells Using Glucose as an Added Growth Substrate

Biodegradation of phenol, a pollutant derived from many industrial processes, was achieved through acclimatized Pseudomonas putida cells. The strategy to overcome the inhibitory effect of phenol on microbial growth involved the addition of glucose, a conventional carbon source. A factorial experimental design was employed in order to optimize the initial phenol and glucose concentrations. The optimum conditions found were applied in 2-lt bioreactors. The development of acclimatized cells and the use of glucose as an added growth substrate resulted in a significant phenol degradation rate of 60.7 mg L−1 h−1 with a complete removal of 1200 mg L−1 phenol.

The inhibitory effects of heavy metals and organic compounds on the net maximum specific growth rate of the autotrophic biomass in activated sludge

A respirometry technique can be applied as an effective method to determine the net maximum specific growth rate of autotrophic biomass under both normal conditions and when inhibition occurs. The net maximum specific growth rate of uninhibited autotrophic biomass, expressed as ( μ ̂ A −b A ), is approximately 0.8 per day [Proceeding of the International Congress on CHISA, Prague, 2002, p. 1]. Several heavy metals and organic compounds have inhibitory effects. Copper (Cu 2+) has stronger inhibitory effects than zinc (Zn 2+), and inhibits the nitrification process by 50% at 0.08 mg/l [( μ ̂ A −b A ) = 0.4 per day], while the same concentration of Zn 2+ establishes 12% inhibition only [( μ ̂ A −b A ) = 0.75 per day]. Inhibition with Cu 2+ starts at concentrations above 0.05 mg/l, while this is above 0.3 mg/l for Zn 2+. The inhibition of the nitrification process is complete at 1.2 mg/l for both Cu 2+ and Zn 2+. Among the selected organic compounds tested in the experiments, the degree of inhibition decreases as follows: chlorobenzene>trichloroethylene (TCE)>phenol>ethylbenzene. Chlorobenzene already inhibits the autotrophic biomass at 0.25 mg/l. The nitrification process is totally inhibited by adding 0.75 mg/l of chlorobenzene. TCE has a less inhibitory effect on the nitrification process and 50% inhibition is noticed at 0.75 mg/l TCE. The nitrification process is totally inhibited at 1 mg/l TCE. Phenol inhibits the nitrification for 50% at 3 mg/l. The inhibitory effect of phenol is almost constant in the range 4–10 mg/l and complete inhibition is reached at 50 mg/l. The inhibitory effect of ethylbenzene is 50% at 8 mg/l and the autotrophic biomass is totally inhibited at 50 mg/l. Experimental findings are compared with literature data, which generally and significantly overestimate the inhibition threshold concentrations.

Determination of phenol using an enhanced chemiluminescent assay.

Enhanced chemiluminescence (ECL) describes the phenomenon of increased light output in the luminol oxidation reaction catalysed by horseradish peroxidase (HRP) in the presence of certain compounds, such as para-iodophenol. In this work, the effects of phenol on the para-iodophenol-enhanced HRP-catalysed chemiluninescent reaction intensity in an aqueous buffer (Tris-HCl buffer, pH 8.5) and in a surfactant-water-octane mixture were compared. Preincubation of HRP at low phenol concentrations stimulated the chemiluminescent intensity in the assay performed in an aqueous buffer, but did not have significant effect in the sodium bis(2-ethylhexyl)sulphosuccinate) (Aerosol OT, AOT) applied system. It was also observed that HRP preincubation with phenol concentration higher than 0.003 mg/mL produced an inhibitory effect on the enzyme activity for both assay systems. Only an inhibitory effect of phenol on the chemiluminescent intensity in the surfactant system in octane (as organic solvent) was observed. Three assays were developed to determine phenol concentration in water and in an organic solvent mixture. The detection limits were 0.006, 0.003 and 0.0005 mg/mL, respectively, for the buffer-containing system, the AOT-applied system with phenol standard solutions in water and for the AOT-applied system with phenol standard solutions in octane.

Development of polysulfone membranes for bacteria immobilization to remove phenol

We have investigated the feasibility of developing polysulfone (PS) membranes to partially immobilize Pseudomonas and to evaluate the inhibitory effect of phenol on immobilized Pseudomonas by monitoring their growths in partially immobilized cell and free-suspension systems. The polysulfone membranes used in this study were wet spun from 20 wt % of PS in 1-methyl-2-pyrrolidone (NMP) solvent using water as the bore fluid as well as the external coagulant. Scanning electron microscopy (SEM) characterization of the newly developed PS hollow fibers suggests that fiber cross-section consists of multilayer microporous structures useful for cell immobilization. Experiments were conducted using Pseudomonas bacteria to remove phenol with initial phenol concentrations of 300 mg/L and 1000 mg/L. In a free suspension (no membrane) system, it was observed that the bacteria were able to grow optimally at 300 mg/L of phenol and degraded phenol almost completely in about 26 h. However, neither cell growth nor phenol degradation occurred when initial concentration of phenol was increased to 1000 mg/L. In a cell-immobilized membrane system, the cell growth and phenol concentration profile in the medium were very similar to those obtained in a free-suspension culture if phenol concentration was 300 mg/L. However, when the initial phenol concentration was increased to 1000 mg/L, data obtained in a cell-immobilized membrane system was discernibly different from that obtained in the suspension culture. In the former case, phenol concentration decreased in the beginning of the test, indicating that the carbon source has been consumed and immobilized cells within the membrane had begun to multiply. As soon as the phenol concentration decreased to about 600 mg/L (at which concentration, substrate inhibition was not as severe as 1000 mg/L), partial immobilization occurred when some cells diffused out of the membrane into the medium and optical density became measurable in the medium. It was found that cell growth continued for the next 28 h, reaching a maximum optical density in the medium of 0.610 absorbance units, and phenol was also completely degraded. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2585–2594, 1998

Chemical composition, in sacco degradation and in vitro gas production of some Ghanaian browse plants

The nutritive value of leaves from four Ghanaian fodder trees, that is, Spondias mombin, Antiaris toxicaria, Baphia nitida and Ficus exasperata and three shrubs, that is, Thespesia populnea, Grewia carpinifolia and Griffornia simplicifolea, were evaluated by chemical, in sacco and in vitro methods. Introduced Gliricidia sepium leaves were included as control feed. Chemical analysis indicated that all samples were high in N (2.84%–4.08%) and low in neutral detergent fibre (NDF) (36.0%–60.6%). With the exception of S. mombin leaves, which had 10.5% total extractable phenolic and 8.6% extractable tannin content, all other tested feeds were low in extractable phenolics (0.56%–3.18%), extractable tannins (0.11%–2.52%) and condensed tannins (<1.21%). Dry matter (DM) and protein degradation after 48 h incubation in sacco ranged from 60.0%–87.5% and 73.1%–93.4%, respectively. B. nitida showed the lowest degradability values (45.7% and 52.5%, respectively). A similar trend was observed from the in vitro gas production data. Use of polyethylene glycol 4000 (phenolic binding agent) indicated that inhibitory effect of phenolics on rumen microbial fermentation was minimal. Data from this study have shown that such Ghanaian browse plants have potential to be used as feed supplements.

Development of cellulose acetate membranes for bacteria immobilization to remove phenol

The objective of this study is to investigate the feasibility of developing cellulose acetate (CA) membranes to partially immobilize Pseudomonas putida (ATCC 49451) and to evaluate the inhibitory effect of phenol on the immobilized bacteria by monitoring their growth in partially immobilized and free-suspension systems. The cellulose acetate membranes used in this study were wet spun from 20 wt % of CA in 1-methyl-2-pyrrolidone (NMP)/acetone (30 : 70) solvent using water as the bore fluid as well as the external coagulant. Scanning-electron microscopy (SEM) characterization of the newly developed CA hollow fibers suggests that the fiber cross section consists of multilayer microporous structures useful for cell immobilization. Experiments were conducted using the bacteria to degrade phenol at initial phenol concentrations of 300 mg/L and 1000 mg/L. In a free suspension (no membrane) system, it was observed that the bacteria were able to grow optimally at 300 mg/L of phenol, and degraded phenol almost completely in about 26 h. However, neither cell growth nor phenol degra- dation occurred when initial concentration of phenol was increased to 1000 mg/L. In a cell-immobilized membrane system, the cell growth and phenol concentration profiles in the medium were very similar to those obtained in a free suspension culture if phenol concentration was 300 mg/L. However, when the initial phenol concentration was increased to 1000 mg/L, data obtained in a cell-immobilized membrane system were discernibly different from that obtained in the suspension culture. In the former case, phenol concentration decreased in the beginning of test, indicating that the carbon source has been consumed and immobilized cells within the membrane had begun to multiply. As soon as the phenol concentration decreased to about 700 mg/L (at which concentration, substrate inhibition was not as severe as 1000 mg/L),partial immobili- zation occurred when some cells diffused out of the membrane into the medium and optical density became measurable in the medium. It was found that cell growth contin- ued for the next 32 h, reaching an optical density in the medium of 0.42 absorbance units and a significant amount of phenol was degraded. q 1998 John Wiley & Sons, Inc.