Parameter optimization and kinetic modelling of phenol degradation using Brevibacillus formosus and Pseudomonas otitidis: design of a bioreactor

Two new high phenol-degrading strains, Micrococcus sp. and Alcaligenes faecalis JH 1013, were isolated. The two isolates could grow aerobically in mineral salts medium containing phenol as a sole carbon source at concentration of 3,000 mg L(-1). It was found that the binary mixed culture of the two isolates possessed good potential for phenol removal. Phenol biodegradation using the binary mixed culture of the two isolates was studied. The optimal conditions were determined to be temperature 32 degrees C, pH 7.0, inoculum size 10.0%, and agitation rate 150 rpm in the synthetic wastewater. In addition, the kinetics of the cell growth and phenol degradation by the binary mixed culture were also investigated using Haldane model over a wide range of initial phenol concentrations from 20 to 2,400 mg L(-1). The experimental data indicated that the binary mixed culture had pretty high phenol degradation potential, which could thoroughly degrade the phenol in the synthetic wastewater containing phenol 2,400 mg L(-1) within 72 h under aerobic condition. Under the optimal conditions, the phenol concentration was reduced speedily from 1,000 to below 0.28 mg L(-1) in the presence of the binary mixed culture, and the phenol degradation rate reached 99.97% after 16 h. It was well below the standard value 0.28 mg L(-1) as described by Chinese Environmental Protection Agency. It was clear that the Haldane kinetic model adequately described the dynamic behavior of phenol degradation by the binary mixed culture with kinetic constants of q (max) = 0.45 h(-1), K (sq) = 64.28 mg L(-1), and K (iq) = 992.79 mg L(-1). The phenol concentration to avoid substrate inhibition had been inferred theoretically to be 252.62 mg L(-1). Phenol, as the only carbon source, could be degraded by the binary mixed culture at high initial phenol concentrations. Phenol exhibited inhibitory behavior, and the growth kinetics of the binary mixed culture could be correlated well by the simple Haldane's inhibitory model. The kinetics parameters were invariably required for the design and simulation of batch and continuous bioreactor treating phenolic wastewaters.

The present study aimed to investigate the effect of initial inoculum size on adventitious root growth and secondary metabolite production in Stevia rebaudiana s root cultures, using various initial inoculum sizes (0.5, 1.0, 1.5, and 2.0 g). The roots were collected from the in-vitro seed-derived plantlets and transferred to a half-strength MS medium with 0.5 mg l−1 naphthalene acetic acid (NAA) to establish adventitious root cultures. Growth kinetics and fresh and dry biomass of adventitious root cultures were enhanced with inoculum size from 0.5–2.0 g. Adventitious root cultures did not show lag phases however, the growth curve was increased at an early stage (day 3) of log phases and sustained for 27 days of culture. The fresh and dry biomass accumulations of the adventitious root cultures were increased by 51 and 120% with 1.5 g inoculum size as compared to a smaller inoculum size (0.5 g). Adventitious root cultures at an initial inoculum size of 2.0 g had a significantly higher content of total phenolics (TPC; 41.46 mg g−1 DW), total flavonoids (TFC; 33.44 mg g−1 DW), and around 98.82% higher potential for scavenging free radicals. In addition, the initial inoculum size of 1.5 g was observed with higher dulcoside contents (0.71 mg g−1 DW), and an inoculum size of 1.0 g was noted with higher content of stevioside (64.75 mg g−1 DW) and rebaudioside (29.67 mg g−1 DW). Therefore, it is concluded that adventitious root cultures accumulated greater fresh and dry biomasses at an inoculum size of 1.5 g, a higher amount of TPC, TFC, and DRSA at 2.0 g, and stevioside and rebaudioside contents at 1.0 g.

In this work the aerobic degradation of phenol by acclimated activated sludge was studied. Results demonstrate that while the phenol removal rate by acclimated activated sludge follows the Monod model, the oxygen uptake rate obeys a Haldane-type equation. The phenol oxidation coefficient obtained at different intial phenol concentrations ranged from 1.9 to 2.6 mol O2 · mol-1 phenol. A mathematical model based on a simplified version of the catalytic mechanism of the enzyme phenol 2-monooxygenase was developed to predict transient phenol concentrations and oxygen requirements by phenol-acclimated activated sludge in batch reactors under different initial phenol concentrations. The proposed model not only adequately represents the experimental results of the present paper, but also those reported by other authors. Particular cases of the proposed model are discussed.Keywords: oxygen uptake rate; phenol; biodegradation; biokinetic model; respirometry

Goat milk is only limited to the processing of goat milk powder and liquid milk, the products are mainly about milk powder and a few of them are made as milk tablet. Therefore, the study of probiotic goat milk will have great significance in the full use of goats and the development of the goat milk industry in China. The effect of fermentation temperature (35°C, 37°C, 39°C), strain ratio (1:1:1, 2:1:1, 3:1:1) and inoculum size (4%, 5%, 6%) on viable counts of L. acidophilus and B. bifidum, total bacteria and sensory value during fermentation process of L. acidophilus and B. bifidum goat yogurt (AB-goat yogurt) was investigated. The optimum fermentation conditions for AB-goat yogurt were: fermentation temperature 38°C, the strain ratio 2:1:1, inoculum size 6%. Under the optimum conditions, the viable counts of B. bifidum, L. acidophilus, total bacteria and sensory value reached (4.30 ±0.11)×107 cfu/mL, (1.39 ±0.09)×108 cfu/mL, (1.82±0.06)×109 cfu/mL and 7.90 ±0.14, respectively. The fermentation temperature, the strain ratio and inoculum size had a significant effect on the fermentation of AB-goat yogurt and these results are beneficial for developing AB-goat yogurt.

Malachite green (MG) dye is a common environmental pollutant that threatens human health and the integrity of the Earth’s ecosystem. The aim of this study was to investigate the potential biodegradation of MG dye by actinomycetes species isolated from planted soil near an industrial water effluent in Cairo, Egypt. The Streptomyces isolate St 45 was selected according to its high efficiency for laccase production. It was identified as S. exfoliatus based on phenotype and 16S rRNA molecular analysis and was deposited in the NCBI GenBank with the gene accession number OL720220. Its growth kinetics were studied during an incubation time of 144 h, during which the growth rate was 0.4232 (µ/h), the duplication time (td) was 1.64 d, and multiplication rate (MR) was 0.61 h, with an MG decolorization value of 96% after 120 h of incubation at 25 °C. Eleven physical and nutritional factors (mannitol, frying oil waste, MgSO4, NH4NO3, NH4Cl, dye concentration, pH, agitation, temperature, inoculum size, and incubation time) were screened for significance in the biodegradation of MG by S. exfoliatus using PBD. Out of the eleven factors screened in PBD, five (dye concentration, frying oil waste, MgSO4, inoculum size, and pH) were shown to be significant in the decolorization process. Central composite design (CCD) was applied to optimize the biodegradation of MG. Maximum decolorization was attained using the following optimal conditions: food oil waste, 7.5 mL/L; MgSO4, 0.35 g/L; dye concentration, 0.04 g/L; pH, 4.0; and inoculum size, 12.5%. The products from the degradation of MG by S. exfoliatus were characterized using high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results revealed the presence of several compounds, including leuco-malachite green, di(tert-butyl)(2-phenylethoxy) silane, 1,3-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, 1,4-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, 1,2-benzenedicarboxylic acid, di-n-octyl phthalate, and 1,2-benzenedicarboxylic acid, dioctyl ester. Moreover, the phytotoxicity, microbial toxicity, and cytotoxicity tests confirmed that the byproducts of MG degradation were not toxic to plants, microbes, or human cells. The results of this work implicate S. exfoliatus as a novel strain for MG biodegradation in different environments.

Bioremediation of wastewater is gaining popularity over chemical treatment due to the greener aspect. The volume of literature containing algal biodegradation is small. Especially, removal of toxic materials like phenol from coke-oven wastewater using fast-growing cyanobacteria was not tried. The current study, therefore, targeted at bioremediation of phenol from wastewater using Leptolyngbya sp., a cyanobacterial strain, as a finishing step. Furthermore, the growth of the strain was studied under different conditions, varying phenol concentration 50-150mg/L, pH 5-11, inoculum size 2-10% to assess its ability to produce lipid. The strain was initially grown in BG-11 as a reference medium and later in phenolic solution. The strain was found to sustain 150mg/L concentration of phenol. SEM study had shown the clear difference in the structure of cyanobacterial strain when grown in pure BG-11 medium and phenolic solution. Maximum removal of phenol (98.5 ± 0.14%) was achieved with an initial concentration 100mg/L, 5% inoculum size at pH 11, while the maximum amount of dry biomass (0.38 ± 0.02g/L) was obtained at pH 7, initial phenol concentration of 50mg/L, and 5% inoculum size. Highest lipid yield was achieved at pH 11, initial phenol concentration of 100mg/L, and 5% inoculum size. Coke-oven wastewater collected from secondary clarifier of effluent treatment plant was also treated with the said strain and the removal of different pollutants was observed. The study suggests the utilization of such potential cyanobacterial strain in treating industrial effluent containing phenol.

Aspergillus niger is considered as the main horsepower for the production of 90% of citric acid worldwide. Citric acid is produced under submerged fermentation and the process yield depends on A. niger and the process parameters. The current research work was aimed to evaluate the most favorable process parameters for producing the highest amount of citric acid using A. niger. The process parameters such as sucrose concentration, pH, temperature, and inoculum size were evaluated for determining their impact on citric acid production. High-performance liquid chromatography (HPLC) analyses revealed different optimal conditions for citric acid production. The optimal conditions found for higher yield of citric acid by A. niger included sucrose concentration 12.0% (w/v), temperature 30 °C, pH 5.0 and an inoculum size of 5.0% (v/v). At these optimal conditions, the resulting concentration was 59.0 g/l of citric acid, 24.0 g/l of biomass production, and 2.0 g/l of residual sugar. In addition, food-grade nature of A. niger was determined by investigating aflatoxin in production media using HPLC. Our results showed that there were no traces of aflatoxins in the production media, hence the used A. niger was of food-grade nature. These findings underline the importance of process evaluation for maximizing citric acid yield and efficiency of A. niger for bioprocess engineering and industrial applications.

Phenol is one of the worst-damaging organic pollutants, and it produces a variety of very poisonous organic intermediates, thus it is important to find efficient ways to eliminate it. One of the promising techniques is sonoelectrochemical processing. However, the type of electrodes, removal efficiency, and process cost are the biggest challenges. The main goal of the present study is to investigate the removal of phenol by a sonoelectrochemical process with different anodes, such as graphite, stainless steel, and titanium. The best anode performance was optimized by using the Taguchi approach with an L16 orthogonal array. the degradation of phenol sonoelectrochemically was investigated with three process parameters: current density (CD) (25, 50, 75, and 100 mA/cm2), time (1, 2, 3, 4 h), and phenol concentration (100, and 200 mg/l). Signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were utilized to examine the impact of each factor. The optimal conditions for phenol removal were 100 mA/cm2, 100 mg/l of phenol, and 4 hours of electrolysis. Under optimal operating conditions, the phenol removal efficiency was 80.99%. The CD was the most influential factor on phenol elimination effectiveness, while the phenol concentration had the least impact.

Fermentative H 2 production was studied using raw POME as the substrate with heat-shock pre-treated POME anaerobic sludge acted as the inoculum. The effect of crucial operating variables (initial pH of medium, incubation temperature, and inoculum size) on H 2 production was studied using Box−Behnken Design. A second-order polynomial regression model was generated to evaluate H 2 production trend under conditions tested. The model analysis revealed the high significance of linear effects of initial pH, incubation temperature, and inoculum size ( P < 0.01) towards H 2 production. Similar results indicated that the interaction effect between initial pH and inoculum size, and interaction effect between incubation temperature and inoculum size were highly significant ( P < 0.01). The regression model suggested that the optimum conditions were set to a pH value, incubation temperature and inoculum size of 6.4, 58.0°C and 8.0% v/v, respectively. In order to validate the optimum conditions determined by the model, heat-shock pre-treated POME anaerobic sludge was incubated with raw POME under optimum conditions. Validation experiment showed that a cumulative H 2 volume of 239.0 mL was produced. Microbial community analysis of inoculum showed that mixed consortia between Clostridium sp. and other obligate anaerobic non-spore forming bacteria, mostly belonging to the Firmicutes and Bacteroidetes phyla were identified as the major H 2 -producers and were hugely responsible towards fermentative H 2 production.

Supercritical carbon dioxide (ScCO2) extraction assisted by Ethanol is one of the development methods to extract polar and nonpolar compounds. Thus, the objective of the study was to optimize extraction parameters to recover total phenolic content (TPC) and total flavonoid content (TFC) from peanut skin. Chrastil, Del Valle Aguilera, and Adachi-Lu models were applied to determine the solubility behaviors. The optimum condition was found at 29.43 MPa, 319.16 K, and 0.09 ml/min with 290.12 mg/L TPC and 488.26 mg/L TFC. Chrastil model gives good agreement to fit the solubility of flavonoid and phenolic contents due to the lowest Average absolute relative deviation were 3.27% and 7.75%, respectively. Practical applications Peanut skin as waste of peanut industries contains high phenolic and flavonoid contents. Currently, conventional extraction process with toxic solvent has been used to extract peanut skin. ScCO2extraction is one of the solutions to break the limitation of solvent's toxicity. However, ScCO2 has the drawbacks that ScCO2 is powerful to extract the nonpolar compounds, but failure to extract the medium polar compounds especially for the flavonoid compounds. Thus, the addition of ethanol is one of development method to break this limitation. Furthermore, Semi-empirical model has been used in this study to determine the solubility behavior to enhance the solubility of phenolic and flavonoid contents. The results show that high temperature condition is suitable to enhance the solubility of TPC, otherwise low temperature condition is preferable in the enhancement of TFC solubility.

Deep eutectic solvent mediated extraction of polysaccharides and antioxidants from Persian manna (Taranjabin): Comparison of different extraction methods and optimization by response surface methodology

The ability of newly isolated bacteria, identified as Bacillus subtilis immobilized on alginate hydrogel beads, to degrade phenol was investigated under different parameters, such as phenol concentration, bead diameter and inoculums size, and was optimized using full factorial design methodology. A mathematical model that governs the degradation of phenol by the immobilized system was obtained and it fitted the experimental data very well. The model indicated that within the range of variables employed, all the parameters and their interactions influenced the biodegradation process, whereby the phenol concentration was the most significant factor. B. subtilis revealed a very high degradation activity and could be grown using phenol as the sole source of carbon. Phenol was degraded by the new bacteria in 8 h under the optimum conditions obtained by the desirability function: 100 mg L-1 phenol concentration, 3 mm beads diameter and 244.5 mg of cell dry per liter biomass size, with a desirability value of 91.25 %.

Analysis of the elemental composition and uptake mechanism of Chlorella sorokiniana for nutrient removal in agricultural wastewater under optimized response surface methodology (RSM) conditions

There is an increasing demand for green chemistry technologies that can cope with environmental waste management challenges. Agro-industrial residues are primarily composed of complex polysaccharides that support microbial growth for the production of industrially important enzymes such as ligninolytic enzymes. Schyzophyllum commune and Ganoderma lucidum were used alone, as well as mixed/co-culture, to produce crude ligninolytic enzymes extracts using corn stover and banana stalk as a substrate during solid state fermentation (SSF). In the initial screening, the extracted ligninolytic enzymes from S. commune produced using corn stover as the substrate showed higher activities of lignin peroxidase (1007.39 U/mL), manganese peroxidase (614.23 U/mL), and laccase (97.47 U/mL) as compared to G. lucidum and the mixed culture. To improve the production of ligninolytic enzymes by S. commune with solid state fermentation (SSF), physical factors such as pH, temperature, moisture, inoculum size, and incubation time were optimized by varying them simultaneously using response surface methodology (RSM) with a central composite design (CCD). The optimum SSF conditions were (for a 5 g corn stover substrate size): pH = 4.5; temperature = 35°C; inoculum size = 4 mL; and moisture content = 60%. Under optimum conditions, the activities of lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase were 1270.40, 715.08, and 130.80 IU/mL, respectively.

Optimization of three parameters, temperature (25-35 degrees C), moisture content (40% (w/v)-60% (w/v) and inoculum sizes (5% (w/v)-15% (w/v) were investigated and optimized by Response Surface Methodology (RSM) for optimal mannanase production by Aspergillus terreus SUK-1. A second order polynomial equation was fitted and the optimum condition was established. The result showed that the moisture content was a critical factor in terms of its effect on mannanase. The optimum condition for mannanase production was predicted at 42.86% (w/v) initial moisture (31 C) temperature and 5.5% (w/v) inoculum size. The predicted optimal parameter were tested in the laboratory and the mannanase activity 45.12 IU mL-1 were recorded to be closed to the predicted value (44.80 IU mL-1). Under the optimized SSF condition (31 degrees C, 42.86% moisture content (w/v) and 5.5% inoculum size (w/v)), the maximum mannanase production was to prevail about 45.12 IU mL-1 compare to before optimized (30 degrees C, 50% moisture content (w/v) and 10% inoculum size (w/v)) was only 34.42 IU mL-1.