IndustrIal BIorefInerIes & WhIte BIotechnology Industrial Biorefineries and White Biotechnology i... more IndustrIal BIorefInerIes & WhIte BIotechnology Industrial Biorefineries and White Biotechnology introduces modern biorefineries as an alternative and as an amendment to industrial crude oil and gas refineries, giving a complete review of the driving forces in modern industrial biotechnology and biochemistry. This book fills a gap in the current knowledge base and will play a key role in advancing technological perspectives in the field. There has been a tremendous amount of recent scientific and technological development in the area of biorefining, including industrial processes and product development using " green technologies, " often referred to as White Biotechnology. This book addresses the requirements for much-needed design concepts in modern biorefineries. Edited by a world-renowned collection of experts, the text merges industrial biorefinery and white biotechnology and is of immense use for students and researchers, including biotechnologists and bioengineers. T...
The aim of this work was to study an externally-submerged membrane bioreactor for the cyclic extr... more The aim of this work was to study an externally-submerged membrane bioreactor for the cyclic extraction of volatile fatty acids (VFAs) during anaerobic fermentation, combining the advantages of submerged and external technologies for enhancing biohydrogen (BioH2) production from agrowaste. Mixing and transmembrane pressure (TMP) across a hollow fiber membrane placed in a recirculation loop coupled to a stirred tank were investigated, so that the loop did not significantly modify the hydrodynamic properties in the tank. The fouling mechanism, due to cake layer formation, was reversible. A cleaning procedure based on gas scouring and backwashing with the substrate was defined. Low TMP, 10(4)Pa, was required to achieve a 3Lh(-1)m(-2) critical flux. During fermentation, BioH2 production was shown to restart after removing VFAs with the permeate, so as to enhance simultaneously BioH2 production and the recovery of VFAs as platform molecules.
Water science and technology : a journal of the International Association on Water Pollution Research, 2005
The presence of a short circuit flow in a denitrifying activated sludge tank was identified and m... more The presence of a short circuit flow in a denitrifying activated sludge tank was identified and modelled. Tracer tests with pulse addition of lithium salt were used to investigate the hydraulics of the tank. The lithium concentration in the effluent was detected and residence time distribution (RTD) curves were generated. Hydraulic models based on completely stirred tank reactors (CSTRs) in series were generated from the RTD curves and the models were compared. The short circuit problem was successfully described using the Martin model, where the inflow is divided into two strands. Each strand was modelled as a number of CSTRs in series. At a normal flow the results of the model show that the tank has 12.8% dead volume, 85.8% main volume and 1.3% short circuiting volume. The inflow was divided into 91.9% entering the main volume and 8.1% entering the short circuiting volume. The mean velocity of the short circuiting stream was estimated to 0.4 m/s. At maximum flow the short circuiti...
Journal of RNAi and gene silencing : an international journal of RNA and gene targeting research, 2011
Rhizopus oryzae is a filamentous fungus, belonging to the order Mucorales. It can ferment a wide ... more Rhizopus oryzae is a filamentous fungus, belonging to the order Mucorales. It can ferment a wide range of carbohydrates hydrolyzed from lignocellulosic materials and even cellobiose to produce ethanol. However, R. oryzae also produces lactic acid as a major metabolite, which reduces the yield of ethanol. In this study, we show that significant reduction of lactic acid production could be achieved by short (25nt) synthetic siRNAs targeting the ldhA gene. The average yield of lactic acid production by R. oryzae during the batch fermentation process, where glucose had been used as a sole carbon source, diminished from 0.07gm/gm in wild type to 0.01gm/gm in silenced samples. In contrast, the average yield of ethanol production increased from 0.39gm/gm in wild type to 0.45gm/gm in silenced samples. These results show 85.7% (gm/gm) reduction in lactic acid production as compared with the wild type R. oryzae, while an increase of 15.4% (gm/gm) in ethanol yield.
Two major hurdles for successful production of second-generation bioethanol are the presence of i... more Two major hurdles for successful production of second-generation bioethanol are the presence of inhibitory compounds in lignocellulosic media, and the fact that Saccharomyces cerevisiae cannot naturally utilise pentoses. There are recombinant yeast strains that address both of these issues, but co-utilisation of glucose and xylose is still an issue that needs to be resolved. A non-recombinant way to increase yeast tolerance to hydrolysates is by encapsulation of the yeast. This can be explained by concentration gradients occuring in the cell pellet inside the capsule. In the current study, we hypothesised that encapsulation might also lead to improved simultaneous utilisation of hexoses and pentoses because of such sugar concentration gradients. In silico simulations of encapsulated yeast showed that the presence of concentration gradients of inhibitors can explain the improved inhibitor tolerance of encapsulated yeast. Simulations also showed pronounced concentration gradients of s...
Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes b... more Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes biogas production when digesting the peels. In this work, pretreatment of the peels to remove limonene under mild condition was proposed by leaching of limonene using hexane as solvent. The pretreatments were carried out with homogenized or chopped orange peel at 20–40°C with orange peel waste and hexane ratio (w/v) ranging from 1 : 2 to 1 : 12 for 10 to 300 min. The pretreated peels were then digested in batch reactors for 33 days. The highest biogas production was achieved by treating chopped orange peel waste and hexane ratio of 12 : 1 at 20°C for 10 min corresponding to more than threefold increase of biogas production from 0.061 to 0.217 m3methane/kg VS. The solvent recovery was 90% using vacuum filtration and needs further separation using evaporation. The hexane residue in the peel had a negative impact on biogas production as shown by 28.6% reduction of methane and lower methane p...
Page 1. Chapter 3 Ethanol from Lignocellulosic Materials: Pretreatment, Acid and Enzymatic Hydrol... more Page 1. Chapter 3 Ethanol from Lignocellulosic Materials: Pretreatment, Acid and Enzymatic Hydrolyses, and Fermentation Mohammad J. Taherzadeh1,2 and Claes Niklasson1 1Department of Chemical Engineering and Environmental ...
Fermentation of lignocellulosic hydrolyzates and other carbon sources to ethanol is affected by d... more Fermentation of lignocellulosic hydrolyzates and other carbon sources to ethanol is affected by different substances present in the cultivation media. High concentration of sugars is desirable in all ethanol processes, in order to have a higher concentration of ethanol, thus reducing the cost of distillation. However, high concentrations of both sugars and ethanol inhibit the fermentation process. Furthermore, high concentration of various salts available in most of the industrial substrates such as sugarcane juice and molasses can also make a ...
Abstract Superabsorbent polymers (SAPs) were prepared from fungal chitosan through three steps of... more Abstract Superabsorbent polymers (SAPs) were prepared from fungal chitosan through three steps of carboxymethylation, cross-linking, and freeze drying. The alkali-insoluble material (AIM) of the cell wall of zygomycetes fungus Rhizomucor pusillus was first pretreated with 72 mM sulfuric acid at room temperature to release the phosphates from the cell wall. The phosphate-free AIM was then either subjected directly to carboxymethylation, or treated with 72 mM sulfuric acid at 120° C to extract and recover the fungal chitosan ...
The ability of macroencapsulated Saccharomyces cerevisiae CBS8066 to withstand readily and not re... more The ability of macroencapsulated Saccharomyces cerevisiae CBS8066 to withstand readily and not readily in situ convertible lignocellulose-derived inhibitors was investigated in anaerobic batch cultivations. It was shown that encapsulation increased the tolerance against readily convertible furan aldehyde inhibitors and to dilute acid spruce hydrolysate, but not to organic acid inhibitors that cannot be metabolized anaerobically. Gene expression analysis showed that the protective effect arising from the encapsulation is evident also on the transcriptome level, as the expression of the stress-related genes YAP1, ATR1 and FLR1 was induced upon encapsulation. The transcript levels were increased due to encapsulation already in the medium without added inhibitors, indicating that the cells sensed low stress level arising from the encapsulation itself. We present a model, where the stress response is induced by nutrient limitation, that this helps the cells to cope with the increased str...
IndustrIal BIorefInerIes & WhIte BIotechnology Industrial Biorefineries and White Biotechnology i... more IndustrIal BIorefInerIes & WhIte BIotechnology Industrial Biorefineries and White Biotechnology introduces modern biorefineries as an alternative and as an amendment to industrial crude oil and gas refineries, giving a complete review of the driving forces in modern industrial biotechnology and biochemistry. This book fills a gap in the current knowledge base and will play a key role in advancing technological perspectives in the field. There has been a tremendous amount of recent scientific and technological development in the area of biorefining, including industrial processes and product development using " green technologies, " often referred to as White Biotechnology. This book addresses the requirements for much-needed design concepts in modern biorefineries. Edited by a world-renowned collection of experts, the text merges industrial biorefinery and white biotechnology and is of immense use for students and researchers, including biotechnologists and bioengineers. T...
The aim of this work was to study an externally-submerged membrane bioreactor for the cyclic extr... more The aim of this work was to study an externally-submerged membrane bioreactor for the cyclic extraction of volatile fatty acids (VFAs) during anaerobic fermentation, combining the advantages of submerged and external technologies for enhancing biohydrogen (BioH2) production from agrowaste. Mixing and transmembrane pressure (TMP) across a hollow fiber membrane placed in a recirculation loop coupled to a stirred tank were investigated, so that the loop did not significantly modify the hydrodynamic properties in the tank. The fouling mechanism, due to cake layer formation, was reversible. A cleaning procedure based on gas scouring and backwashing with the substrate was defined. Low TMP, 10(4)Pa, was required to achieve a 3Lh(-1)m(-2) critical flux. During fermentation, BioH2 production was shown to restart after removing VFAs with the permeate, so as to enhance simultaneously BioH2 production and the recovery of VFAs as platform molecules.
Water science and technology : a journal of the International Association on Water Pollution Research, 2005
The presence of a short circuit flow in a denitrifying activated sludge tank was identified and m... more The presence of a short circuit flow in a denitrifying activated sludge tank was identified and modelled. Tracer tests with pulse addition of lithium salt were used to investigate the hydraulics of the tank. The lithium concentration in the effluent was detected and residence time distribution (RTD) curves were generated. Hydraulic models based on completely stirred tank reactors (CSTRs) in series were generated from the RTD curves and the models were compared. The short circuit problem was successfully described using the Martin model, where the inflow is divided into two strands. Each strand was modelled as a number of CSTRs in series. At a normal flow the results of the model show that the tank has 12.8% dead volume, 85.8% main volume and 1.3% short circuiting volume. The inflow was divided into 91.9% entering the main volume and 8.1% entering the short circuiting volume. The mean velocity of the short circuiting stream was estimated to 0.4 m/s. At maximum flow the short circuiti...
Journal of RNAi and gene silencing : an international journal of RNA and gene targeting research, 2011
Rhizopus oryzae is a filamentous fungus, belonging to the order Mucorales. It can ferment a wide ... more Rhizopus oryzae is a filamentous fungus, belonging to the order Mucorales. It can ferment a wide range of carbohydrates hydrolyzed from lignocellulosic materials and even cellobiose to produce ethanol. However, R. oryzae also produces lactic acid as a major metabolite, which reduces the yield of ethanol. In this study, we show that significant reduction of lactic acid production could be achieved by short (25nt) synthetic siRNAs targeting the ldhA gene. The average yield of lactic acid production by R. oryzae during the batch fermentation process, where glucose had been used as a sole carbon source, diminished from 0.07gm/gm in wild type to 0.01gm/gm in silenced samples. In contrast, the average yield of ethanol production increased from 0.39gm/gm in wild type to 0.45gm/gm in silenced samples. These results show 85.7% (gm/gm) reduction in lactic acid production as compared with the wild type R. oryzae, while an increase of 15.4% (gm/gm) in ethanol yield.
Two major hurdles for successful production of second-generation bioethanol are the presence of i... more Two major hurdles for successful production of second-generation bioethanol are the presence of inhibitory compounds in lignocellulosic media, and the fact that Saccharomyces cerevisiae cannot naturally utilise pentoses. There are recombinant yeast strains that address both of these issues, but co-utilisation of glucose and xylose is still an issue that needs to be resolved. A non-recombinant way to increase yeast tolerance to hydrolysates is by encapsulation of the yeast. This can be explained by concentration gradients occuring in the cell pellet inside the capsule. In the current study, we hypothesised that encapsulation might also lead to improved simultaneous utilisation of hexoses and pentoses because of such sugar concentration gradients. In silico simulations of encapsulated yeast showed that the presence of concentration gradients of inhibitors can explain the improved inhibitor tolerance of encapsulated yeast. Simulations also showed pronounced concentration gradients of s...
Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes b... more Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes biogas production when digesting the peels. In this work, pretreatment of the peels to remove limonene under mild condition was proposed by leaching of limonene using hexane as solvent. The pretreatments were carried out with homogenized or chopped orange peel at 20–40°C with orange peel waste and hexane ratio (w/v) ranging from 1 : 2 to 1 : 12 for 10 to 300 min. The pretreated peels were then digested in batch reactors for 33 days. The highest biogas production was achieved by treating chopped orange peel waste and hexane ratio of 12 : 1 at 20°C for 10 min corresponding to more than threefold increase of biogas production from 0.061 to 0.217 m3methane/kg VS. The solvent recovery was 90% using vacuum filtration and needs further separation using evaporation. The hexane residue in the peel had a negative impact on biogas production as shown by 28.6% reduction of methane and lower methane p...
Page 1. Chapter 3 Ethanol from Lignocellulosic Materials: Pretreatment, Acid and Enzymatic Hydrol... more Page 1. Chapter 3 Ethanol from Lignocellulosic Materials: Pretreatment, Acid and Enzymatic Hydrolyses, and Fermentation Mohammad J. Taherzadeh1,2 and Claes Niklasson1 1Department of Chemical Engineering and Environmental ...
Fermentation of lignocellulosic hydrolyzates and other carbon sources to ethanol is affected by d... more Fermentation of lignocellulosic hydrolyzates and other carbon sources to ethanol is affected by different substances present in the cultivation media. High concentration of sugars is desirable in all ethanol processes, in order to have a higher concentration of ethanol, thus reducing the cost of distillation. However, high concentrations of both sugars and ethanol inhibit the fermentation process. Furthermore, high concentration of various salts available in most of the industrial substrates such as sugarcane juice and molasses can also make a ...
Abstract Superabsorbent polymers (SAPs) were prepared from fungal chitosan through three steps of... more Abstract Superabsorbent polymers (SAPs) were prepared from fungal chitosan through three steps of carboxymethylation, cross-linking, and freeze drying. The alkali-insoluble material (AIM) of the cell wall of zygomycetes fungus Rhizomucor pusillus was first pretreated with 72 mM sulfuric acid at room temperature to release the phosphates from the cell wall. The phosphate-free AIM was then either subjected directly to carboxymethylation, or treated with 72 mM sulfuric acid at 120° C to extract and recover the fungal chitosan ...
The ability of macroencapsulated Saccharomyces cerevisiae CBS8066 to withstand readily and not re... more The ability of macroencapsulated Saccharomyces cerevisiae CBS8066 to withstand readily and not readily in situ convertible lignocellulose-derived inhibitors was investigated in anaerobic batch cultivations. It was shown that encapsulation increased the tolerance against readily convertible furan aldehyde inhibitors and to dilute acid spruce hydrolysate, but not to organic acid inhibitors that cannot be metabolized anaerobically. Gene expression analysis showed that the protective effect arising from the encapsulation is evident also on the transcriptome level, as the expression of the stress-related genes YAP1, ATR1 and FLR1 was induced upon encapsulation. The transcript levels were increased due to encapsulation already in the medium without added inhibitors, indicating that the cells sensed low stress level arising from the encapsulation itself. We present a model, where the stress response is induced by nutrient limitation, that this helps the cells to cope with the increased str...
Uploads
Papers by Mohammad J . Taherzadeh