The retting of flax after preservation with sulphur dioxide

Experiments were carried out to compare the retting of moist flax preserved with sulphur dioxide with that of green dried flax, using whole straw samples. When retted in water at either a constant 20°C or 28°C dried flax was fully retted after 15 and 10 days respectively whereas the sulphur dioxide treated flax (20 g sulphur dioxide kg“¹ flax DM) had undergone almost no retting after 20 days at 20dC or 10 days at 28°C. Pre-soaking the treated flax for 24 h in water and changing the acidified water, raised the pH of the retting liquor to a more normal value but did not significantly increase the rate of retting. Addition of the pectinase enzyme preparation ‘Flaxzyme’ to retting liquor at the rate of either 1.5 g kg^-1 or 3.0 g kg^-1 water, and at a constant temperature of 20°C, substantially increased the rate of retting of both sulphur dioxide treated and dried flax. Optimum degree of retting was achieved at 24 h with the treated flax and at 97 h with the dried flax. Pre-rinsing of the sulphur dioxide treated straw only served to reduce the rate of retting. It was concluded that natural water retting of sulphur dioxide treated flax is retarded by the presence of acidic residues of sulphur dioxide, while enzyme retting is enhanced by these. In further smaller scale experiments using bundles of cut flax straw Flaxzyme was added at concentrations ranging from 0–8.0 ml litre ¹ to containers containing flax in water at ratios from 1:10 to 1: 600 flax:water and the producion of galacturonic acid was used as an indicator of retting progress. Retting took place more rapidly at higher flax to water ratios for a given enzyme concentration. This effect was attributed to the lower pH of higher flax to water ratios which created pH conditions closer to the pH optimum for the retting enzymes. When enzyme retting was compared at a range of buffered pH's the optimum was pH 4.0. At a buffered pH of 4.0 and a temperature of 19°C, retting of sulphur dioxide treated moist flax (flax to water ratio of 1:10) was achieved with Flaxzyme concentrations as low as 0.5 ml litre”‘,much lower than the previously reported minimum of 3.0 ml litre’.     

Bioabsorption of chromium from retan chrome liquor by cyanobacteria

The bioaccumulation of chromium from retan chrome liquor by Spirulina fusiformis was investigated under laboratory as well as field conditions. At the optimal conditions, metal ion uptake increased with initial metal ion concentration up to 300 mg/l. The effect on various physico-chemical parameters like total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), chlorides, sulphates, phenols, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) and biochemical studies related to biomass, chlorophyll-a and protein were also carried out. The present study indicates that S. fusiformis is very effective in removal of chromium (93–99%) besides removing other toxicants from retan chrome liquor. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and FTIR studies indicate the interaction/complexation between Cr and alga. The mechanism involved in bioaccumulation of chromium is also discussed. The process when upgraded can be applied for detoxification of tannery effluents.     

Chemical retting of flax using chelating compounds

A wide range of concentrations of ethylenediaminetetra acetic acid (EDTA) was tested as a retting agent at a range of temperatures, pHs and stem: liquor ratios. Treatment of stems at 2 and 3 g/litre at 40 °C in a liquor ratio of 1:10 at pH 11 produced the finest and strongest fibre. Dried-green stem retted slightly better than the glyphosate-desiccated stem and after multiple retting with EDTA, Trilon TB and diethyltriaminepenta acetic acid (DTPA), the dried-green stem produced the finest fibre. Trilon TB and DTPA retted better than EDTA and produced a high yield of fibres. The fluidity of fibres scutched from the dried-green stem was lower than the fluidity of the fibres from glyphosate-desiccated stem.     

Analysis of retted and non retted flax fibres by chemical and enzymatic means

Flax fibres (Linum usitatissimum L.) were subjected to chemical and enzymatic analysis in order to determine the compositional changes brought about by the retting process and also to determine the accessibility of the fibre polymers to enzymatic treatment. Chemical analysis involved subjecting both retted and non retted fibres to a series of sequential chemical extractions with 1% ammonium oxalate, 0.05 M KOH, 1 M KOH and 4 M KOH. Retting was shown to cause minimal weight loss from the fibres but caused significant changes to the pectic polymers present. Retted fibres were shown to have significantly lower amounts of rhamnogalacturonan as well as arabinan and xylan. In addition the average molecular mass of the pectic extracts was considerably lowered. Enzyme treatment of the 1 M KOH extracts with two different enzymes demonstrated that the non retted extract contained a relatively high molecular weight xylan not found in the retted extract. Treatment of the 1 M KOH extracts and the fibres with Endoglucanase V from Trichoderma viride demonstrated that while this enzyme solubilised cellulose as well as xylan and xyloglucan oligomers from the extract, it had limited access to these polymers on the fibre. MALDI-TOF MS analysis of the material solubilised from the extract suggested that the xylan was randomly substituted with 4-O-methyl glucuronic acid moieties. The xyloglucan was shown to be of the XXXG type and was substituted with galactose and fucose units. The enzyme treatments of the fibres demonstrated that the xylan and xyloglucan polymers in the fibres were not accessible to the enzyme but that material which was entrapped by the cellulose could be released by the hydrolysis of this cellulose.     

An alternative method of flax retting during dry weather

During exceptionally dry and hot weather undesiccated flax (Linum usitatissi-murri) and flax desiccated with glyphosate that was pulled and laid on the ground to dew-ret, retted 1–2 wk before flax that was desiccated and left as a standing crop. This was because dew-retted flax was colonised by fungi faster than that left standing. Cladosporium herbarum, Epicocum nigrum and yeast, including Aureoba-sidium pullulans, appeared first; they were followed by Alternaria alternata, Fusarium culmorum and Phoma, Mucor and Rhizopus species. The standing crop retted more slowly despite the presence of greater concentrations of cell-wall degrading enzymes. However, the fibres of flax retted as a standing crop retained more of their strength than those of flax retted on the ground. Thus dew-retting provides means of retting when the weather is dry and hot.     

Pollution control in pulp and paper industrial effluents using integrated chemical–biological treatment sequences

The main objective of the present study was to improve the quality of pulp and paper industrial wastewater of two local mills RAKTA and El-Ahlia, Alexandria, Egypt, and to bring their pollutant contents to safe discharge levels. Quality improvement was carried out using integrated chemical and biological treatment approaches after their optimization. Chemical treatment (alum, lime, and ferric chloride) was followed by oxidation using hydrogen peroxide and finally biological treatment using activated sludge (90 min for RAKTA and 60 min for El-Ahlia effluents). Chemical coagulation produced low-quality effluents, while pH adjustment during coagulation treatment did not enhance the quality of the effluents. Maximum removal of the tested pollutants was achieved using the integrated treatment and the pollutants recorded residual concentrations (RCs) of 34.67, 17.33, 0.13, and 0.43 mg/l and 15.0, 11.0, 0.0, and 0.13 mg/l for chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), tannin and lignin, and silica in RAKTA and El-Ahlia effluents, respectively, all of which were below their maximum permissible limits (MPLs) for the safe discharge into water courses. Specific oxygen uptake rate (SOUR) and sludge volume index (SVI) values reflect good conditions and healthy activated sludge. Based on the previous results, optimized conditions were applied as bench scale on the raw effluents of RAKTA and El-Ahlia via the batch chemical and the biological treatment sequences proposed. For RAKTA effluents, the sequence was as follows: (1) coagulation with 375 mg/l FeCl₃, (2) oxidation with 50 mg/l hydrogen peroxide, and (3) biological treatment using activated sludge with 2,000 mg/l initial concentration and 90 min hydraulic retention time (HRT), while for El-Ahlia raw effluents, the sequence was (1) coagulation with 250 mg/l FeCl₃, (2) oxidation with 45 mg/l hydrogen peroxide, and (3) biological treatment using activated sludge with 2,000 mg/l initial concentration and 60 min HRT. In conclusion, results confirmed that the application of the proposed sequential treatments removed almost all COD, BOD₅, high molecular weight compounds, and silica from RAKTA and El-Ahlia influents and produced high-quality effluents, thus achieving the main objective of this study.     

An integrated treatment system for coffee processing wastewater using anaerobic and aerobic process

The experiment was conducted to develop an integrated treatment system for coffee processing wastewater (CPWW) through the combination of biomethanation with aeration and wetland plants treatment. The biomethanation was carried out at different hydraulic retention times (HRTs) using upflow anaerobic hybrid reactor (UAHR) and 18 h of HRT was found to be optimum. The maximum biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total solids (TS) reduction were 66.0%, 61.0% and 58.0%, respectively with organic loading rate of 9.55 kg m^?3 day^?1. The reduction of pollution load of the wastewater by microbial action augmented by aeration resulted in the reduction of electrical conductivity (EC), BOD, COD, and total solids (TS). Continuous aeration of wastewater resulted in maximum reduction of BOD (74.6%), COD (68.6%) and TS (49.3%). The wetland plant, Typha latifolia reduced 85.4% and 78.0% of BOD and COD, respectively in biomethanated cum aerated CPWW.     

Effects of selected pectinolytic bacterial strains on water-retting of hemp and fibre properties

Aims:  To study the effect of selected bacterial strains on hemp water-retting and properties of retted fibre.
Methods and Results:  The trials were performed in laboratory tanks. The traditional water-retting process, without inoculum addition, was compared to a process modified by inoculating water tanks with two selected pectinolytic bacteria: the anaerobic strain Clostridium sp. L1/6 and the aerobic strain Bacillus sp. ROO40B. Six different incubation times were compared. Half the fibre obtained from each tank was combed. Micromorphological analyses were performed by scanning electron microscopy on uncombed and combed fibres. Moreover, organoleptic and chemical analyses of uncombed fibres were performed.
Conclusions:  The inoculum , besides speeding up the process, significantly improved the fibre quality. The fibre was not damaged by mechanical hackling, thanks to the good retting level obtained by the addition of selected strains, differently to what happened with the traditionally retted fibre. The best fibre quality was obtained after 3–4 days of retting with the addition of the bacterial inoculum .
Significance and Impact of the Study:  Retting is the major limitation to an efficient production of high-quality hemp fibres. The water-retting process and fibre quality were substantially improved by simultaneously inoculating water tanks with two selected pectinolytic strains.     

Comparison of subjective and objective methods to assess flax straw cultivars and fibre quality after dew-retting

Subjective and objective methods were compared for the assessment of the quality of unretted and retted straw, and the fibres obtained after dew-retting of four flax cultivars, Ariane, Evelin, Laura and Viola. Maturity of straw, degree of retting, ease of decortication after retting, divisibility, handle, cleanliness and colour were assessed as subjective factors and of these, degree of retting and handle appear to be useful for assessing quality. The samples were also analysed for physical and chemical differences using a range of objective methods. Straw quality could not be graded using height and maturity, although stem diameter and technical length could indicate quality. Changes in N, lipid and ash content, as a result of retting, were observed. The increase in the proportions of fibre fractions present in retted compared with unretted straw, due to microbial degradation of pectin, could be identified by thermal analysis. Analyses of the fibre samples to determine fineness, strength, cellulose, hemicellulose, lignin and minerals were carried out and significant differences in some of the parameters were identified. Cultivar Laura produced the best fibre. Fibre fineness, ash, lipid, caustic weight loss and fibre fractions as determined by thermal analysis were found to be important objective parameters for quality assessment. The assessment of fibre samples performed subjectively by an expert grader and by selected objective methods gave similar quality rankings.     

Reduction in Acute Ecotoxicity of Paper Mill Effluent by Sequential Application of Xylanase and Laccase

In order to reduce the ecotoxicity of paper mill, four different enzymatic pretreatment strategies were investigated in comparison to conventional chemical based processes. In strategy I, xylanase-aided pretreatment of pulp was carried out, and in strategy II, xylanase and laccase-mediator systems were used sequentially. Moreover, to compare the efficiency of Bacillus stearothermophilus xylanase and Ceriporiopsis subvermispora laccase in the reduction of ecotoxicity and pollution, parallel strategies (III and IV) were implemented using commercial enzymes. Conventional C_DE_OPD₁D₂ (C_D, Cl₂ with ClO₂; E_OP, H₂O₂ extraction; D₁ and D_2, ClO₂) and X/XLC_DE_OPD₁D₂ (X, xylanase; L, laccase) sequences were employed with non-enzymatic and enzymatic strategies, respectively. Acute toxicity was determined by the extent of inhibition of bioluminescence of Vibrio fischeri with different dilutions of the effluent. Two-fold increase was observed in EC₅₀ values for strategy I compared to the control process. On the other hand, sequential application of commercial enzymes resulted in higher acute toxicity compared to lab enzymes. In comparison to the control process, strategy II was the most efficient and successfully reduced 60.1 and 25.8% of biological oxygen demand (BOD) and color of effluents, respectively. We report for the first time the comparative analysis of the ecotoxicity of industrial effluents.     

Improving retting of fibre through genetic modification of flax to express pectinases

Flax (Linum usitatissimum L.) is a raw material used for important industrial products. Linen has very high quality textile properties, such as its strength, water absorption, comfort and feel. However, it occupies less than 1% of the total textile market. The major reason for this is the long and difficult retting process by which linen fibres are obtained. In retting, bast fibre bundles are separated from the core, the epidermis and the cuticle. This is accomplished by the cleavage of pectins and hemicellulose in the flax cell wall, a process mainly carried out by plant pathogens like filamentous fungi. The remaining bast fibres are mainly composed of cellulose and lignin. The aim of this study was to generate plants that could be retted more efficiently. To accomplish this, we employed the novel approach of transgenic flax plant generation with increased polygalacturonase (PGI ) and rhamnogalacturonase (RHA) activities. The constitutive expression of Aspergillus aculeatus genes resulted in a significant reduction in the pectin content in tissue-cultured and field-grown plants. This pectin content reduction was accompanied by a significantly higher (more than 2-fold) retting efficiency of the transgenic plant fibres as measured by a modified Fried’s test. No alteration in the lignin or cellulose content was observed in the transgenic plants relative to the control. This indicates that the over-expression of the two enzymes does not affect flax fibre composition. The growth rate and soluble sugar and starch contents were in the range of the control levels. It is interesting to note that the RHA and PGI plants showed higher resistance to Fusarium culmorum and F. oxysporum attack, which correlates with the increased phenolic acid level. In this report, we demonstrate for the first time that over-expression of the A. aculeatus genes results in flax plants more readily usable for fibre production. The biochemical parameters of the cell wall components indicated that the fibre quality remains similar to that of wild-type plants, which is an important pre-requisite for industrial applications. Magdalena Musialak and Magdalena Wróbel-Kwiatkowska participated equally in the preparation of this paper     

Side-by-side comparison of horizontal subsurface flow and free water surface flow constructed wetlands and artificial neural network (ANN) modelling approach

A horizontal subsurface flow (HSSF) and a free water surface flow (FWSF) constructed wetlands (4 m² of each) were set up on the campus of Harran University, Sanliurfa, Turkey. The main objective of the research was to compare the performance of two systems to decide the better one for future planning of wastewater treatment system on the campus. Both of the wetland systems were planted with Phragmites australis and Canna indica. During the observation period (10 months), environmental conditions such as pH, temperature and total chemical oxygen demand (COD), soluble COD, total biochemical oxygen demand (BOD), soluble BOD, total suspended solids (TSS), total phosphate (TP), total nitrogen (TN) removal efficiencies of the systems were determined. According to the results, average yearly removal efficiencies for the HSSF and the FWSF, respectively, were as follows: total COD (75.7% and 69.9%), soluble COD (85.4% and 84.3%), total BOD (79.6% and 87.6%), soluble BOD (87.7% and 95.3%), TN (33.2% and 39.4%), and TP (31.5% and 6.5%). Soluble COD and BOD removal efficiencies of both systems increased gradually since the start-up. After nine months of operation, above 90% removal of organic matters were observed. The treatment performances of the HSSF were better than that of the FWSF with regard to the removal of suspended solids and total COD at especially high temperatures. In FWSF systems, COD concentrations extremely exceeded the discharge limit values due to high concentrations of algae in spring months.The performance of the two systems was modelled using an artificial neural network-back-propagation algorithm. The ANN model was competent at providing reasonable match between the measured and the predicted concentrations of total COD (R = 0.90 for HSSF and R = 0.96 for FWSF), soluble COD (R = 0.90 for HSSF and R = 0.74 for FWSF) and total BOD (R = 0.94 for HSSF and R = 0.84 for FWSF) in the effluents of constructed wetlands.     

Impact of fly ash pretreatment on aerobic treatment of thermomechanical pulping spent liquor

This study investigated the impact of biomass‐based fly ash (FA) pretreatment on the biodegradability of a thermomechanical pulping spent liquor (TMPL) in an aerobic system. In this study, FA was mixed with TMPL under the conditions of 6 wt.% based on TMPL, 25°C and 10 h, which removed a part of recalcitrant organic materials and resulted in 68.0, 40.0, 60.1, 81.2 and 48.3% reductions in chemical oxygen demand (COD), biochemical oxygen demand (BOD), total organic carbon (TOC), lignin and sugar, respectively. FA‐pretreated TMPL pressate (FA‐TMPL) was biologically treated in an aerobic system of sequencing batch reactor (SBR). The performance of the biological treatment with and without FA pretreatment was studied in two parallel SBRs over three months. The combination of FA and biological treatments removed 97.3% of COD, 98.3% of BOD, 96.3% of lignin, 99.5% of sugar, and 98.1% of TOC. Without FA pretreatment, the biological system removed 87.3% of COD, 89% of BOD, 81.6% of lignin, 98.6% of sugars, and 90.5% of TOC. The results also confirmed that the settling ability of sludge, which was indicated as a sludge volume index, was reduced from 109.3 mL/g to 53.5 mL/g. In addition, the advantages of using FA pretreatment in aerobic systems were discussed in detail. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:370–378, 2018     

Removal of organic pollutants and analysis of MLSS–COD removal relationship at different HRTs in a submerged membrane bioreactor

In order to investigate the influence of hydraulic retention time (HRT) on organic pollutant removal in a submerged membrane bioreactor (SMBR), a laboratory-scale experiment was conducted using domestic sewage as influent. The dissolved oxygen (DO) concentration was controlled at 2.0– during the experimental period. The experiments demonstrated that when HRT was 3, 2 and 1 h, the reduction of chemical oxygen demand (COD) was 89.3–97.2, 88.5–97.3 and 80–91.1%, and the effluent COD was 38.9–11.2, 41.6–10.8 and 63.4–, respectively. It is suggested that an HRT of 1 h could meet the normal standard of discharged domestic sewage, and an HRT of 2 h could meet that of water reclamation. In addition, we use mathematical software MATLAB to analyse the relation of mixed liquor suspended solids (MLSS) and COD removal. The results showed that the optimum MLSS concentration should be maintained at around in the SMBR. The results also showed that the COD removal was related to HRT (τ), influent concentration (S₀) and sludge loading rate for COD removal (N_S). Moreover, the high COD removal could be achieved through adjusting τ, S₀ and N_S.     

Phytoremediation of wastewater toxicity using water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes)

This paper elucidates the phytoremediation potential of water hyacinth and water lettuce on the reduction of wastewater toxicity. Acute toxicity tests were performed in an aquarium with a population of Sarotherodon melanotheron, contaminated by different concentrations of wastewaters before and after phytoremediation with Eichhornia crassipes and Pistia stratiotes. Lethal concentrations (LC₅₀) of the fish's population obtained during 24 hours of exposures were determined. COD, BOD, ammonium, TKN and PO₄^3? concentrations in wastewaters were of 1850.29, 973.33, 38.34, 61.49 and 39.23 mg L^?1, respectively, for each plant. Phytoremediation reduced 58.87% of ammonium content, 50.04% of PO₄^3?, 82.45% of COD and 84.91% of BOD. After 15 days of the experiment, metal contents in treated wastewaters decreased from 6.65 to 97.56% for water hyacinth and 3.51 to 93.51% for water lettuce tanks. Toxicity tests showed that the mortality of fish exposed increased with increase in concentration of pollutants in wastewaters and the time of exposure. Therefore, the highest value of LC₅₀ was recorded for fish subjected to 3 hours of exposure (16.37%). The lowest rate was obtained after an exposure of 20 to 24 hours (5.85%). After phytoremediation, the effluents purified by Eichhornia crassipes can maintain the fish life beyond 24 hours of exposure.     

Anaerobic treatment of wastewater with high suspended solids from a bulk drug industry using fixed film reactor (AFFR)

Studies were carried out on the treatment of wastewater from a bulk drug industry using an anaerobic fixed film reactor (AFFR) designed and fabricated in the laboratory. The chemical oxygen demand (COD) and total dissolved solids (TDS) of the wastewater were found to be very high with low biochemical oxygen demand (BOD) to COD ratio and high total suspended solid (TSS) concentration. Acclimatization of seed consortia and startup of the reactor was carried out by directly using the wastewater, which resulted in reducing the period of startup to 30 days. The reactor was studied at different organic loading rates (OLR) and it was found that the optimum OLR was 10 kg COD/m(3)/day. The wastewater under investigation, which had a considerable quantity of SS, was treated anaerobically without any pretreatment. COD and BOD of the reactor outlet wastewater were monitored and at steady state and optimum OLR 60-70% of COD and 80-90% of BOD were removed. The reactor was subjected to organic shock loads at two different OLR and the reaction could withstand the shocks and performance could be restored to normalcy at that OLR. The results obtained indicated that AFFR could be used efficiently for the treatment of wastewater from a bulk drug industry having high COD, TDS and TSS.     

Hydrogen peroxide as a supplemental oxygen source for activated sludge: Microbiological investigations

Summary Parallel bench-scale activated sludge systems were operated using air or hydrogen peroxide as oxygen source. The use of H₂O₂ resulted in a temporary decrease of COD reduction, an increase of the catalase activity of the activated sludge, a depression of the nitrification, and a marked decrease of some filamentous organisms. Enumeration of some microbiologic groups indicated that the counts of enterobacteria, coliforms, staphylococci, and streptococci were lower in the H₂O₂ unit than in the parallel air unit. Also the use of H₂O₂ did not induce the selection of bacterial species that are more resistant to H₂O₂. The increase in catalase activity after H₂O₂ addition might be the result of a stimulation of catalase synthesis in catalase positive microorganisms.List of Abbreviation COD chemical oxygen demand, mg O₂/1 - COD_eff chemical oxygen demand of the effluent, mg O₂/1 - DO dissolved oxygen, mg O₂/1 - MLSS mixed liquor suspended solids, g dry weight/1 - SVI sludge volume index, ml settled sludge per liter/MLSS (ml/g) - F:M sludge loading factor or the Food to Microorganisms ratio, g COD/g MLSS.day     

Comparison between biological and chemical treatment of wastewater containing nitrogen and phosphorus

The present work compared chemical and biological treatment methods to achieve the most efficient treatment for the reduction or elimination of phosphorus and nitrogen from mixed industrial–domestic wastewaters. Batch chemical precipitation by ferric chloride and aluminum sulfate (alum) and a continuous biological suspended growth system were investigated as well as the optimum operating conditions. Concerning chemical treatment, Alum generally achieved a higher removal efficiency percentage for the investigated pollutants compared with FeCl₃ at their optimum pH and dose, especially with chemical oxygen demand (COD). FeCl₃ treatment achieved success only with phosphorus removal, while none of the COD, 5-day biochemical oxygen demand (BOD₅), total nitrogen (TN) and N–NH₃ achieved acceptable treatment and remained above the maximum permissible limits (MPL). Thus, for such wastewaters, alum is more efficient than FeCl₃. Biological treatment exhibited higher efficiencies, particularly towards nitrogen. TN removal increased by increasing the flow rate to 30–60 l/day. N–NH₃ removal was effective at the slowest flow rate and decreased with increasing flow rate, while an opposite trend was recorded for N–NO₃. At all flow rates, phosphorus levels were below the accepted MPL for discharging into natural systems. Moreover, there was a general trend for the proposed biological treatment to achieve a high removal efficiency for BOD₅ and COD, bringing them to acceptable levels to be released into watercourses safely, especially at the slowest flow rates. Thus, integration between the proposed chemical and biological treatment is highly recommended, producing high-quality effluents acceptable by the environmental law.     

Study on microbe retting of kenaf fiber

Retting is the predominant problem in the application of kenaf fiber in high-grade products. While the traditional retting method is water retting, that is, the harvested bast kenaf is immersed in natural water (rivers or tanks) in which indigenous bacteria colonize noncellulosic materials in an anaerobic process resulting in severe environmental problems and low-grade fiber, therefore it is inevitable to seek for a pollution-free or little-pollution retting method. With the more application of biotechnology in textile industry, the more biology-treatments have been researched recently. So microbe retting was employed in this work. The fungus strain was isolated from the river in which kenaf fiber was retted, then microbe retting was performed with this fungus. Substrate species, the initial pH of the culture medium, cultivation temperature, retting time and inoculum size are involved in the experiments and the evaluation of retting is based on the residual gum content in retted kenaf fiber. As a result, the removal of pectin in microbe retting of kenaf is 91.31% under the optimal retting conditions. In addition, the effective retting fungus is also observed with microscope as one kind of filamentous epiphyte.     

Reduction of phenolics content and COD in olive oil mill wastewaters by indigenous yeasts and fungi

Olive oil mill wastewaters (OOMW) cause a recurrent environmental pollution problem. The large concentration of phenolic compounds in the organic fraction of OOMW is principally responsible for the phytotoxicity and microbial growth inhibitory effects of the effluent. Candida boidinii, Geotrichum candidum, a Penicillium sp. and Aspergillus niger HA37 were isolated from OOMW. When cultivated directly on an undiluted OOMW-based medium containing 82 g l⁻¹ COD, these strains removed only 4–8% of chemical oxygen demand (COD) and phenolics. In contrast, reduction values attaining respectively 40–73% for phenolics and 45–78% for COD removal in the undiluted OOMW-based medium were obtained when using the strains gradually acclimated to high concentration of OOMW by successive stepwise transfer from media containing COD of 20.5 up to 82 g l⁻¹. Possibly, a sufficient production level of degradation and/or detoxification enzymes has to be attained to overcome the toxic effects of the phenolic fraction of concentrated OOMW. The present investigation calls attention to the necessity of acclimation for certain fungal and yeasts strains potentially useful for treating highly polluted effluents.