Papers by Najafpour Prof. Ghasem
Lactobacillus plantarum, as a potential lactic acid and protease producer, was used for biologica... more Lactobacillus plantarum, as a potential lactic acid and protease producer, was used for biological extraction of chitin from shrimp shell. L. plantarum was grown in a batch culture containing shrimp shell powder and date syrup, incubated at 30 °C. The produced organic acids and proteases in L. plantarum culture were able to demineralize and deproteinize shrimp shell. Percentages of deproteinization and demineralization were 45 and 54, respectively. In post treatment of the sample, dilute acid and alkali, were implemented to produce the specific chitin.
In this study, the capabilities of response surface methodology (RSM) and artificial neural netwo... more In this study, the capabilities of response surface methodology (RSM) and artificial neural networks (ANN) for modeling and optimization of ethanol production from glucose using Saccharomyces cerevisiae in batch fermentation process were investigated. The effects of three independent variables in a defined range of pH (4.2-5.8), temperature (20-40 °C) and glucose concentration (20-60 g/l) on the cell growth and ethanol production were evaluated. The results showed that the prediction accuracy of ANN was apparently similar to RSM. At optimum conditions of temperature (32 °C), pH (5.2) and glucose concentration (50 g/l), suggested by the statistical methods, the maximum cell dry weight and ethanol concentration obtained from RSM were 12.06 and 16.2 g/l, whereas experimental values were 12.09 and 16.53 g/l, respectively. The present study showed that using ANN as a fitness function, the maximum cell dry weight and ethanol concentration were 12.05 and 16.16 g/l, respectively. Also, the coefficients of determination for biomass and ethanol concentration obtained from RSM were 0.9965 and 0.9853 and from ANN were 0.9975 and 0.9936, respectively. The process parameters optimization was successfully conducted using RSM and ANN; however, prediction by ANN was slightly more precise than RSM. Based on experimental data, the maximum yield of ethanol production of 0.5 g ethanol/g substrate (97% of theoretical yield) was obtained.
Removal of melanoidin pigment from molasses spent wash was investigated using a new adsorbent. So... more Removal of melanoidin pigment from molasses spent wash was investigated using a new adsorbent. Solid
adsorbents were fabricated from charcoal fly ash and clay. The effect of various molasses concentration (6 to 12 g/l)
on removal efficiency was studied. The obtained results revealed that maximum removal efficiency of 82% was achieved
at the molasses concentration of 6 g/l and contact time of 7 h. The saturated porous adsorbents were regenerated and
reused to conduct similar experiments. The achieved data showed that more than 90% of the capacity of the fresh adsorbent
was recovered after regeneration. Various adsorption isotherms of Langmuir, Freundlich, Temkin and Harkins-
Jura were applied to interpret the obtained experimental data. The obtained results revealed that the sorption data were
well described by the Harkins-Jura model. Also, various kinetic models of pseudo-first order, pseudo-second order,
Elovich and intra-particle diffusion were used to predict the characteristic parameters which are useful in process design.
It was concluded that the best fit was obtained with pseudo-second order kinetic model at low molasses concentrations.
An environmentally friendly method with the aid of biomaterials was used to determine glucose in ... more An environmentally friendly method with the aid of biomaterials was used to determine glucose in aqueous
solutions. For this purpose, an electrochemical biosensor was fabricated by modifying the platinum
electrode. The drop-dry deposition was used to immobilize enzyme on the surface of electrode. Glucose
oxidase (GOx) was selected as the enzyme due to its excellent affinity to glucose. Then to immobilize GOx
the electrode was coated by chitosan (CHIT) which is a biopolymer derived from chitin. Cyclic voltammetric
experiment was carried out in absence and presence of glucose in 0.1 M phosphate buffer (PB) solution.
Analysis of the cyclic voltammograms indicated that a catalytic reaction occurred on the modified electrode
which was resulted from the oxidation of glucose by GOx. The electroactive surface area of the modified
electrode was assessed by the cyclic voltammetry in 1 M KCl solution containing 5 mM K3[Fe(CN)6] at scan
rates of 10-100 mVs−1 and calculated to be 0.012 cm2. Amperometric measurements were performed with an
applied potential of +0.75 V at 25±0.2 °C in 0.1 M PB solution containing variable concentrations of glucose.
The modified electrode showed an excellent performance for glucose detection with a high sensitivity of 38.5
μA mM−1 cm−2 and the detection limit of 17.4 μM glucose. The effect of temperature on the biosensor
response and also the stability of biosensor were investigated. The fabricated biosensor showed accurate,
fast and reliable responses for detection of glucose in aqueous phase.
Kinetic studies of the enzymatic hydrolysis of molasses were conducted using glucoamylase. Centra... more Kinetic studies of the enzymatic hydrolysis of molasses were conducted using glucoamylase. Central Sugar Refinery SDN BHD contains 13–20% glucose. The molasses was diluted and the kinetic experiments were conducted at 67 C with 100–1000 mg/l of glucoamylase. The glucose contents of the molasses were enhanced after hydrolysis of molasses solution with 1000 mg/l glucoamylase. A Lineweaver–Burk plot was obtained based on enzyme kinetic data. The rate constant, Km and maximum reaction rate, Vmax for 500 mg/l of glucoamylase were 100 mmol/l (18 g/l) and 5 mmol/l min (0.9 g/l min), respectively. The maximum reaction rate, Vmax for 1000 mg/l of glucoamylase was doubled, to 100 mmol/l (18 g/l) and the rate constant, Km was the same for 500 mg/l of glucoamylase. The substrate inhibition model was noncompetitive based on the resulting Lineweaver–Burk plot for enzyme concentration of 500 and 1000 mg/l.
Fermentation of sugar by Saccharomyces cerevisiae, for production of ethanol in an immobilized ce... more Fermentation of sugar by Saccharomyces cerevisiae, for production of ethanol in an immobilized cell reactor (ICR) was successfully carried out to improve the performance of the fermentation process. The fermentation set-up was comprised of a column packed with beads of immobilized cells. The immobilization of S. cerevisiae was simply performed by the enriched cells cultured media harvested at exponential growth phase. The fixed cell loaded ICR was carried out at initial stage of operation and the cell was entrapped by calcium alginate. The production of ethanol was steady after 24 h of operation. The concentration of ethanol was affected by the media flow rates and residence time distribution from 2 to 7 h. In addition, batch fermentation was carried out with 50 g/l glucose concentration. Subsequently, the ethanol productions and the reactor productivity of batch fermentation and immobilized cells were compared. In batch fermentation, sugar consumption and ethanol production obtained were 99.6% and
12.5% v/v after 27 h while in the ICR, 88.2% and 16.7% v/v were obtained with 6 h retention time. Nearly 5% ethanol production
was achieved with high glucose concentration (150 g/l) at 6 h retention time. A yield of 38% was obtained with 150 g/l glucose. The yield was improved approximately 27% on ICR and a 24 h fermentation time was reduced to 7 h. The cell growth rate was based on the Monod rate equation. The kinetic constants (Ks and Vm) of batch fermentation were 2.3 g/l and 0.35 g/l h, respectively. The maximum yield of biomass on substrate (YX=S) and the maximum yield of product on substrate (YP=S) in batch fermentations were 50.8% and 31.2% respectively. Productivity of the ICR were 1.3, 2.3, and 2.8 g/l h for 25, 35, 50 g/l of glucose concentration, respectively. The productivity of ethanol in batch fermentation with 50 g/l glucose was calculated as 0.29 g/l h. Maximum production
of ethanol in ICR when compared to batch reactor has shown to increase approximately 10-fold. The performance of the two
reactors was compared and a respective rate model was proposed. The present research has shown that high sugar concentration (150 g/l) in the ICR column was successfully converted to ethanol. The achieved results in ICR with high substrate concentration are promising for scale up operation. The proposed model can be used to design a lager scale ICR column for production of high ethanol concentration.
Biological treatment using attached growth on a rotating biological contactor (RBC) was used for ... more Biological treatment using attached growth on a rotating biological contactor (RBC) was used for the wastewater from Palm Oil Mill
industries, which contains high strength of organic compounds, COD of about 16,000 mg/l. An acclimated Saccharomyces cerevisiae with
POME was used as the initial biomass for the attached growth on bio-discs. After 5 days, 91% BOD removal was achieved in a batch
experiment. Eighty-eight percent removal of COD was obtained with 55 h HRT. High surface COD loading of 38–210 g COD/m2 day was
implemented. Eighty percent TKN and 89% SS removal were obtained in the bench scale RBC. The maximum specific growth rate and the
reaction rate were 0.82 day1 and 0.3 m3/m2 day, respectively. The high organic loading of POME has been treated successfully in a bench
scale RBC.
In design of anaerobic bioreactor, rate equation is commonly used. Mathematical
model was develop... more In design of anaerobic bioreactor, rate equation is commonly used. Mathematical
model was developed at steady state condition, to project concentration of gaseous
substrate and product in biological oxidation of carbon monoxide with water to produce
hydrogen and carbon dioxide. The concept of bioconversion was based on transport of CO
from gas phase to liquid phase, as the CO consumption was instantaneous and the moles of
CO in liquid phase was oxidized to CO2,and H2 was liberated from water. The moles of
produced H2 were identical to the moles of CO transported to the fermentation media. The
data was experimentally obtained in a continuous stirred tank bioreactor. A photosynthetic
bacterium, Rhodospirillum rubrum, was used as biocatalyst to facilitate the oxidization of
carbon monoxides via water-gas shift reaction. The rate of CO consumption and hydrogen
production were projected based on dynamic model at steady state condition. The
experimental data were fitted to a few rate models and the best suitable dynamic model for
hydrogen production was obtained. The model was used for scale up calculation and
dependency of the rate equation and the model to a few process variables were analyzed.
The liquid phase medium was supplied for microbial growth with initial concentration of
4 g / l . The media flow rate to the reactor space time (F/VL) was 0.2 h-1. At the steady state
condition, the concentration of acetate was independent of the dilution rate and it was
approximated about 1.5 g / l .
A bench-scale anaerobic bioreactor for the anaerobic treatment of textile wastewater using anaero... more A bench-scale anaerobic bioreactor for the anaerobic treatment of textile wastewater using anaerobic sludge was experimented. The Top and bottom of hybrid bioreactor were functioned with UAF (Up Flow Anaerobic Filter) and UASB (Up Flow Anaerobic Sludge Blanket), respectively. The effect of organic loading rate (OLR) and hydraulic retention time (HRT) on treatment of organic matters in the textile wastewater was investigated. The maximum removal of chemical oxygen demand (COD) and color was 94.8 and 84.4%, respectively. Biogas production and methane yields were determined. Maximum gas production rate of 36 L/d was achieved. The purity of biogas in terms of methane content was 79%. The ratio of Mixed Liquor Volatile Suspended Solids/Mixed Liquor Suspended Solids (MLVSS/MLSS) in the hybrid system was reduced from 0.72 to 0.61 during 180 days of operation.
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Papers by Najafpour Prof. Ghasem
adsorbents were fabricated from charcoal fly ash and clay. The effect of various molasses concentration (6 to 12 g/l)
on removal efficiency was studied. The obtained results revealed that maximum removal efficiency of 82% was achieved
at the molasses concentration of 6 g/l and contact time of 7 h. The saturated porous adsorbents were regenerated and
reused to conduct similar experiments. The achieved data showed that more than 90% of the capacity of the fresh adsorbent
was recovered after regeneration. Various adsorption isotherms of Langmuir, Freundlich, Temkin and Harkins-
Jura were applied to interpret the obtained experimental data. The obtained results revealed that the sorption data were
well described by the Harkins-Jura model. Also, various kinetic models of pseudo-first order, pseudo-second order,
Elovich and intra-particle diffusion were used to predict the characteristic parameters which are useful in process design.
It was concluded that the best fit was obtained with pseudo-second order kinetic model at low molasses concentrations.
solutions. For this purpose, an electrochemical biosensor was fabricated by modifying the platinum
electrode. The drop-dry deposition was used to immobilize enzyme on the surface of electrode. Glucose
oxidase (GOx) was selected as the enzyme due to its excellent affinity to glucose. Then to immobilize GOx
the electrode was coated by chitosan (CHIT) which is a biopolymer derived from chitin. Cyclic voltammetric
experiment was carried out in absence and presence of glucose in 0.1 M phosphate buffer (PB) solution.
Analysis of the cyclic voltammograms indicated that a catalytic reaction occurred on the modified electrode
which was resulted from the oxidation of glucose by GOx. The electroactive surface area of the modified
electrode was assessed by the cyclic voltammetry in 1 M KCl solution containing 5 mM K3[Fe(CN)6] at scan
rates of 10-100 mVs−1 and calculated to be 0.012 cm2. Amperometric measurements were performed with an
applied potential of +0.75 V at 25±0.2 °C in 0.1 M PB solution containing variable concentrations of glucose.
The modified electrode showed an excellent performance for glucose detection with a high sensitivity of 38.5
μA mM−1 cm−2 and the detection limit of 17.4 μM glucose. The effect of temperature on the biosensor
response and also the stability of biosensor were investigated. The fabricated biosensor showed accurate,
fast and reliable responses for detection of glucose in aqueous phase.
12.5% v/v after 27 h while in the ICR, 88.2% and 16.7% v/v were obtained with 6 h retention time. Nearly 5% ethanol production
was achieved with high glucose concentration (150 g/l) at 6 h retention time. A yield of 38% was obtained with 150 g/l glucose. The yield was improved approximately 27% on ICR and a 24 h fermentation time was reduced to 7 h. The cell growth rate was based on the Monod rate equation. The kinetic constants (Ks and Vm) of batch fermentation were 2.3 g/l and 0.35 g/l h, respectively. The maximum yield of biomass on substrate (YX=S) and the maximum yield of product on substrate (YP=S) in batch fermentations were 50.8% and 31.2% respectively. Productivity of the ICR were 1.3, 2.3, and 2.8 g/l h for 25, 35, 50 g/l of glucose concentration, respectively. The productivity of ethanol in batch fermentation with 50 g/l glucose was calculated as 0.29 g/l h. Maximum production
of ethanol in ICR when compared to batch reactor has shown to increase approximately 10-fold. The performance of the two
reactors was compared and a respective rate model was proposed. The present research has shown that high sugar concentration (150 g/l) in the ICR column was successfully converted to ethanol. The achieved results in ICR with high substrate concentration are promising for scale up operation. The proposed model can be used to design a lager scale ICR column for production of high ethanol concentration.
industries, which contains high strength of organic compounds, COD of about 16,000 mg/l. An acclimated Saccharomyces cerevisiae with
POME was used as the initial biomass for the attached growth on bio-discs. After 5 days, 91% BOD removal was achieved in a batch
experiment. Eighty-eight percent removal of COD was obtained with 55 h HRT. High surface COD loading of 38–210 g COD/m2 day was
implemented. Eighty percent TKN and 89% SS removal were obtained in the bench scale RBC. The maximum specific growth rate and the
reaction rate were 0.82 day1 and 0.3 m3/m2 day, respectively. The high organic loading of POME has been treated successfully in a bench
scale RBC.
model was developed at steady state condition, to project concentration of gaseous
substrate and product in biological oxidation of carbon monoxide with water to produce
hydrogen and carbon dioxide. The concept of bioconversion was based on transport of CO
from gas phase to liquid phase, as the CO consumption was instantaneous and the moles of
CO in liquid phase was oxidized to CO2,and H2 was liberated from water. The moles of
produced H2 were identical to the moles of CO transported to the fermentation media. The
data was experimentally obtained in a continuous stirred tank bioreactor. A photosynthetic
bacterium, Rhodospirillum rubrum, was used as biocatalyst to facilitate the oxidization of
carbon monoxides via water-gas shift reaction. The rate of CO consumption and hydrogen
production were projected based on dynamic model at steady state condition. The
experimental data were fitted to a few rate models and the best suitable dynamic model for
hydrogen production was obtained. The model was used for scale up calculation and
dependency of the rate equation and the model to a few process variables were analyzed.
The liquid phase medium was supplied for microbial growth with initial concentration of
4 g / l . The media flow rate to the reactor space time (F/VL) was 0.2 h-1. At the steady state
condition, the concentration of acetate was independent of the dilution rate and it was
approximated about 1.5 g / l .
adsorbents were fabricated from charcoal fly ash and clay. The effect of various molasses concentration (6 to 12 g/l)
on removal efficiency was studied. The obtained results revealed that maximum removal efficiency of 82% was achieved
at the molasses concentration of 6 g/l and contact time of 7 h. The saturated porous adsorbents were regenerated and
reused to conduct similar experiments. The achieved data showed that more than 90% of the capacity of the fresh adsorbent
was recovered after regeneration. Various adsorption isotherms of Langmuir, Freundlich, Temkin and Harkins-
Jura were applied to interpret the obtained experimental data. The obtained results revealed that the sorption data were
well described by the Harkins-Jura model. Also, various kinetic models of pseudo-first order, pseudo-second order,
Elovich and intra-particle diffusion were used to predict the characteristic parameters which are useful in process design.
It was concluded that the best fit was obtained with pseudo-second order kinetic model at low molasses concentrations.
solutions. For this purpose, an electrochemical biosensor was fabricated by modifying the platinum
electrode. The drop-dry deposition was used to immobilize enzyme on the surface of electrode. Glucose
oxidase (GOx) was selected as the enzyme due to its excellent affinity to glucose. Then to immobilize GOx
the electrode was coated by chitosan (CHIT) which is a biopolymer derived from chitin. Cyclic voltammetric
experiment was carried out in absence and presence of glucose in 0.1 M phosphate buffer (PB) solution.
Analysis of the cyclic voltammograms indicated that a catalytic reaction occurred on the modified electrode
which was resulted from the oxidation of glucose by GOx. The electroactive surface area of the modified
electrode was assessed by the cyclic voltammetry in 1 M KCl solution containing 5 mM K3[Fe(CN)6] at scan
rates of 10-100 mVs−1 and calculated to be 0.012 cm2. Amperometric measurements were performed with an
applied potential of +0.75 V at 25±0.2 °C in 0.1 M PB solution containing variable concentrations of glucose.
The modified electrode showed an excellent performance for glucose detection with a high sensitivity of 38.5
μA mM−1 cm−2 and the detection limit of 17.4 μM glucose. The effect of temperature on the biosensor
response and also the stability of biosensor were investigated. The fabricated biosensor showed accurate,
fast and reliable responses for detection of glucose in aqueous phase.
12.5% v/v after 27 h while in the ICR, 88.2% and 16.7% v/v were obtained with 6 h retention time. Nearly 5% ethanol production
was achieved with high glucose concentration (150 g/l) at 6 h retention time. A yield of 38% was obtained with 150 g/l glucose. The yield was improved approximately 27% on ICR and a 24 h fermentation time was reduced to 7 h. The cell growth rate was based on the Monod rate equation. The kinetic constants (Ks and Vm) of batch fermentation were 2.3 g/l and 0.35 g/l h, respectively. The maximum yield of biomass on substrate (YX=S) and the maximum yield of product on substrate (YP=S) in batch fermentations were 50.8% and 31.2% respectively. Productivity of the ICR were 1.3, 2.3, and 2.8 g/l h for 25, 35, 50 g/l of glucose concentration, respectively. The productivity of ethanol in batch fermentation with 50 g/l glucose was calculated as 0.29 g/l h. Maximum production
of ethanol in ICR when compared to batch reactor has shown to increase approximately 10-fold. The performance of the two
reactors was compared and a respective rate model was proposed. The present research has shown that high sugar concentration (150 g/l) in the ICR column was successfully converted to ethanol. The achieved results in ICR with high substrate concentration are promising for scale up operation. The proposed model can be used to design a lager scale ICR column for production of high ethanol concentration.
industries, which contains high strength of organic compounds, COD of about 16,000 mg/l. An acclimated Saccharomyces cerevisiae with
POME was used as the initial biomass for the attached growth on bio-discs. After 5 days, 91% BOD removal was achieved in a batch
experiment. Eighty-eight percent removal of COD was obtained with 55 h HRT. High surface COD loading of 38–210 g COD/m2 day was
implemented. Eighty percent TKN and 89% SS removal were obtained in the bench scale RBC. The maximum specific growth rate and the
reaction rate were 0.82 day1 and 0.3 m3/m2 day, respectively. The high organic loading of POME has been treated successfully in a bench
scale RBC.
model was developed at steady state condition, to project concentration of gaseous
substrate and product in biological oxidation of carbon monoxide with water to produce
hydrogen and carbon dioxide. The concept of bioconversion was based on transport of CO
from gas phase to liquid phase, as the CO consumption was instantaneous and the moles of
CO in liquid phase was oxidized to CO2,and H2 was liberated from water. The moles of
produced H2 were identical to the moles of CO transported to the fermentation media. The
data was experimentally obtained in a continuous stirred tank bioreactor. A photosynthetic
bacterium, Rhodospirillum rubrum, was used as biocatalyst to facilitate the oxidization of
carbon monoxides via water-gas shift reaction. The rate of CO consumption and hydrogen
production were projected based on dynamic model at steady state condition. The
experimental data were fitted to a few rate models and the best suitable dynamic model for
hydrogen production was obtained. The model was used for scale up calculation and
dependency of the rate equation and the model to a few process variables were analyzed.
The liquid phase medium was supplied for microbial growth with initial concentration of
4 g / l . The media flow rate to the reactor space time (F/VL) was 0.2 h-1. At the steady state
condition, the concentration of acetate was independent of the dilution rate and it was
approximated about 1.5 g / l .