Papers by Dr-Malek Alkasrawi
On the performance of real grey water treatment using a submerged membrane bioreactor system, Jou... more On the performance of real grey water treatment using a submerged membrane bioreactor system, Journal of Membrane Science, http://dx.
The present paper investigated the technical possibilities of bioethanol production from coffee p... more The present paper investigated the technical possibilities of bioethanol production from coffee pulp in a sustainable manner. Coffee pulp is a largely underutilized waste stream and has the potential to become a bioethanol feedstock if processing is economically viable. This study aimed to characterize the chemical composition of coffee pulp with relevance to bioethanol production and to compare results to other bioethanol feedstocks. Based on the total sugar yield, we investigated bioethanol production using AspenPlus simulation software. In the sugar characterization part, total carbohydrates were measured after complete acid hydrolysis of dry pulp, while water-soluble carbohydrates were measured after acid hydrolysis of soxhlet extracted solutions. Moisture, lignin, and ash contents were measured gravimetrically after appropriate heating treatments. The results showed sugar contents, expressed as percentages of dry mass, as follows: 5.8, 5.2, 20.2, 4.2, and 4.7 % for arabinose, galactose, glucose, xylose, and mannose, respectively. Arabinose, galactose, and glucose were the only water-extracted simple sugars, at 1.0, 1.4, and 2.6 % of dry mass, respectively. AspenPlus simulation was based on processing 10,000 ton/day of coffee pulp. The results demonstrated sugar and ethanol yield of 2100 and 1050 ton/day, respectively. This would make annually profit of $0.13 million. The simulation estimated the capital investment cost was about $2 million. In order to satisfy the process economy, the process operation cost must be operated at minimum of $1.87 million annually. The life-cycle analysis showed the net value of energy of the whole process is an economical as well as the balance of CO 2 emission/reduction was on the environmental favor.
A microbial biosensor based on immobilised psychrotrophic yeast Yarrowia lipolytica integrated to... more A microbial biosensor based on immobilised psychrotrophic yeast Yarrowia lipolytica integrated to FIA for the determination of middle chain alkanes was developed. The system responded very well to middle chain alkanes even at low operational temperatures down to +5°C. The maximum sensitivity was obtained at 15°C. A linear relationship was observed between the sensor response and dodecane concentration up to 100 mM.
Yeast to be used in simultaneous saccharification and fermentation (SSF) of lignocelluloses mater... more Yeast to be used in simultaneous saccharification and fermentation (SSF) of lignocelluloses materials has to be prepared in a separate cultivation step. The effects of the cultivation procedure on the performance of SSF of steam pretreated softwood were studied in the current work. The yeast used in the SSF was either directly commercially available Baker's yeast (as packaged yeast) or the same strain of yeast produced from the hydrolysate obtained in the pretreatment of the softwood material. A second strain of Saccharomyces cerevisiae TMB3000, isolated from spent sulphite liquor, was also compared with the commercial Baker's yeast. The strains were tested in SSF at substrate loads of 3, 5 and 8% dry weight of water insoluble material. Final ethanol yields were above 85% of the theoretical (based on the available hexoses) in all cases, except for the package yeast for the 8% substrate load, in which case the final yield was less than 65%. The cultivation procedure was found to have a significant impact on the performance during SSF, as well as in small-scale fermentations of hydrolysate liquor without solid material. The Baker's yeast cultivated on the hydrolysate from the steam pretreatment had in all cases a higher productivity, in particular at the highest substrate load. Cultivated Baker's yeast had a slightly higher productivity than TMB3000. The results suggest that the adaptation of the yeast to the inhibitors present in the medium is an important factor that must be considered in the design of SSF processes.
. The amount of glucose hydrolyzed over a 72 hour incubation period using a variety of enzyme dos... more . The amount of glucose hydrolyzed over a 72 hour incubation period using a variety of enzyme dosages (20µL/g=blue, 50µL/g=red, 80µL/g=green) Compared to the maximum mg glucose per gram dry weight of sludge(purple).
Simultaneous saccharification and fermentation (SSF) of steam-pretreated wood constitutes an attr... more Simultaneous saccharification and fermentation (SSF) of steam-pretreated wood constitutes an attractive process configuration for ethanol production from biomass. However, the high enzyme addition in SSF contributes to a high process cost. In this study we explore the effect of the non-ionic surfactant Tween-20 as an additive in SSF. Tween-20 addition at 2.5 g/l had several positive effects on SSF: (i) the ethanol yield was increased by 8%; (ii) the amount of enzyme loading could be reduced by 50%, while maintaining a constant yield; (iii) the enzyme activity increased in the liquid fraction at the end of SSF, probably by preventing unproductive binding of the cellulases to lignin, which could facilitate enzyme recovery; (iv) the time required to attain maximum ethanol concentration was reduced. Surfactants as an additive in SSF can significantly lower the operational cost of the process. However, less expensive surfactants must be investigated.
In order to improve the process economy it is important to use as high dry matter content as poss... more In order to improve the process economy it is important to use as high dry matter content as possible in simultaneous saccharification and fermentation (SSF). However, too high dry matter content often gives rise to severe inhibition of the yeast metabolism, due to the increased levels of toxic compounds. The aim of the present work was to increase the fibrous content in SSF of steam pretreated spruce to 10% by adapting the yeast to the inhibitory substrate and by using a fed-batch process. Both batch and fed-batch approaches were evaluated. The fed-batch experiments were started with a batch fermentation containing 6% dry matter. Fibrous slurry from the pretreatment was then added four times during the first 24 h giving a final dry matter content corresponding to 10%. The yeast used in the fermentation was produced aerobically on the hemicellulose hydrolysate obtained from the pretreatment. SSF batch and fed-batch experiments with a cell mass concentration of 2, 3 and 5 g/L were carried out. When adapted yeast was used, the available hexoses were completely converted within 72 h and the final ethanol concentrations reached 40-44 g/L. No major differences in performance between batch and fed-batch were seen, but the ethanol productivity during the first 24 h was higher in the fed-batch SSF experiments, particularly during the experiments with a cell mass concentration of 2 and 3 g/L. .se (A. Rudolf). the concentrations of compounds inhibitory to yeast and enzymes are simultaneously increased. In addition, the rheological properties of a very dense fibrous suspension may cause mixing and heat transfer problems.
Effect of condensate streams recirculation on the ethanol yield was investigated. Recycling of co... more Effect of condensate streams recirculation on the ethanol yield was investigated. Recycling of condensate stream exhibits no effect on ethanol yield or productivity. Recycling of condensate stream replaced totally the addition of fresh water. The proposed configuration diminishes the problem of lactic acid production.
The effect of process stream recirculation on ethanol production from steam-pretreated softwood b... more The effect of process stream recirculation on ethanol production from steam-pretreated softwood based on simultaneous saccharification and fermentation (SSF) was investigated for two process configurations. In the first configuration, a part of the stillage stream after distillation was recycled and, in the second configuration, the liquid after SSF was recycled. The aim was to minimize the energy consumption in the distillation of the fermentation broth and in the evaporation of the stillage, as well as the use of fresh water. However, recirculation leads to an increased concentration of nonvolatiles in the first configuration, and of both volatiles and nonvolatiles in the second configuration. These substances might be inhibitory to the enzymes and the yeast in SSF. When 60% of the fresh water was replaced by stillage, the ethanol yield and the productivity were the same as for the configuration without recirculation. The ethanol production cost was reduced by 17%. In the second configuration, up to 40% of the fresh water could be replaced without affecting the final ethanol yield, although the initial ethanol productivity decreased. The ethanol production cost was reduced by 12%. At higher degrees of recirculation, fermentation was clearly inhibited, resulting in a decrease in ethanol yield while hydrolysis seemed unaffected.
Effect of condensate streams recirculation on the ethanol yield was investigated. Recycling of co... more Effect of condensate streams recirculation on the ethanol yield was investigated. Recycling of condensate stream exhibits no effect on ethanol yield or productivity. Recycling of condensate stream replaced totally the addition of fresh water. The proposed configuration diminishes the problem of lactic acid production.
High removal of heavy metal ions from metal plating wastewater using EC treatment. Pseudo first-o... more High removal of heavy metal ions from metal plating wastewater using EC treatment. Pseudo first-order kinetic model describes heavy metal ions removal adequately. Electrocoagulation time and DC current density are the key parameters in EC process. Metal plating wastewater treatment by electrocoagulation is economically rewarding.
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Papers by Dr-Malek Alkasrawi