Abdel E. Ghaly

Phytoaccumulation of heavy metals by aquatic plants

Three aquatic plants were examined for their ability to remove heavy metals from contaminated water: parrot feather (Myriophylhum aquaticum), creeping primrose (Ludwigina palustris), and water mint (Mentha aquatic). The plants were obtained from a Solar Aquatic System treating municipal wastewater. All the three plants were able to remove Fe, Zn, Cu, and Hg from the contaminated water. The average removal efficiency for the three plant species was 99.8%, 76.7%, 41.62%, and 33.9% of Hg, Fe, Cu, and Zn, respectively. The removal rates of zinc and copper were constant (0.48 mg/l/day for Zn and 0.11 mg/l/day for Cu), whereas those of iron and mercury were dependent on the concentration of these elements in the contaminated water and ranged from 7.00 to 0.41 mg/l/day for Fe and 0.0787 to 0.0002 mg/l/day for Hg. Parrot feather showed greater tolerance to toxicity followed by water mint and creeping primrose. The growth of creeping primrose was significantly affected by heavy metal toxicity. The selectivity of heavy metals for the three plant species was the same (Hg>Fe>Cu>Zn). The mass balance preformed on the system showed that about 60.45-82.61% of the zinc and 38.96-60.75% of the copper were removed by precipitation as zinc phosphate and copper phosphate, respectively.

Microalgae Harvesting Methods for Industrial Production of Biodiesel: Critical Review and Comparative Analysis

Microalgae biomass can be used to produce numerous value added products such as biodiesel, bioethanol, biogas and bio hydrogen, fish feed, animal feed, human food supplements and skin care products. Production of value added products from microalgae biomass requires growing and recovery of the algae biomass and extraction and downstream processing of the desired product. However, the major obstacle for using microalgae biomass on an industrial-scale for the production of biodiesel and other value added products is the dewatering step which accounts for 20-30% of the total costs associated with microalgae production and processing. The aim of this study was to review the current methods used for harvesting and concentrating microalgae and to perform a comparative analysis in order to determine the most efficient and economically viable dewatering methods for large scale processing of microalgae biomass. The harvesting techniques investigated included sedimentation, vacuum filtration, pressure filtration, cross flow filtration, disc stack centrifugation, decanter centrifuge, dispersed air floatation, dissolved air flotation, fluidic oscillation, inorganic flocculation, organic flocculation, auto-flocculation, bio-flocculation electrolytic coagulation, electrolytic flocculation and electrolytic floatation. Eight criteria were used for evaluation of these microalgae harvesting techniques: (a) dewatering efficiency (b) cost (c) toxicity (d) suitability for industrial scale (e) time (f) species specificity (g) reusability of media and (h) maintenance. Each criterion was assigned a score between 7 and 15 based on its degree of importance. Higher values were given to the criteria that were deemed most important for development of an efficient and economic large scale dewatering method for microalgae whereas lower values were given to criteria that were deemed necessary for determining a suitable method but were considered less important. The results indicated that of the 16 methods evaluated, 4 scored values of 80/100 and above and were deemed suitable for harvesting microalgae on an industrial scale. Three were physical techniques (disc stack centrifuge (87/100), cross flow filtration (84/100), decanter centrifugation (82/100)) and the forth was the organic flocculation (80) method. These techniques were deemed suitable for large scale use because of their effectiveness, low operational costs, suitability for numerous species, rapidness, minimal maintenance requirement and being environmentally friendly. The other methods were deemed unsuitable because they are not effective in dewatering a wide array of microalgae species, not suited for large volumes, costly and require high maintenance. Although each of the optimum techniques was deemed suitable for harvesting of microalgae on its merit, a combination of methods can also be used to enhance the recovery efficiency and improve the economics. The use of organic flocculation as an initial harvesting step to concentrate the algae suspension and the centrifugation (or filtration) as a secondary dewatering step will reduce the time and costs associated with dewatering. Flocculation allows for effective removal of algae from large amounts of liquid media and as such the costs associated with energy intensive centrifugation and filtration techniques (used individually) can be reduced by using them as secondary techniques since less volumes of microalgae suspension will undergo the secondary treatment.

Extraction of Proteins from Mackerel Fish Processing Waste Using Alcalase Enzyme

Fish proteins are found in the flesh, head, frames, fin, tail, skin and guts of the fish in varying quantities. Unutilized fish and fish processing waste can be used to produce fish proteins which contain amino acids and many bioactive peptides. After removing the fish flesh during the fish processing operation, all other parts are considered wastes which are not properly utilized. The aim of this study was to evaluate the enzymatic extraction of protein from mackerel fish processing waste. Enzymatic extraction of proteins was carried out using alcalase enzyme at three concentrations (0.5, 1 or 2%) and four hydrolysis times (1, 2, 3 and 4 h). The fish protein hydrolysate was dried using a spray dryer to obtain protein powder. The highest protein yield (76.30% from whole fish and 74.53% from the frame) was obtained using 2.0% enzyme concentration after 4 h of hydrolysis. The results showed that increasing the enzyme concentration from 0.5 to 2% (400%) increased the protein yield by 3.13- 43.52% depending upon the fish part and reaction time used. Increasing the enzyme concentration by 4 fold for a small increase in protein yield may appear unjustified. Therefore, the enzyme concentration of 0.5% should be used for the protein extraction unless the enzyme is recycled or an immobilized reactor is used in order to reduce the cost associated with the enzyme. Also, increasing the hydrolysis time from 1 to 4 h (400%) increased the protein yield by 16.45 - 50.82% depending upon the fish part and enzyme concentration used. Increasing the hydrolysis time by 4 fold for a small increase in protein yield will increase the capital and operating costs of protein production. A shorter hydrolysis time will allow more throughput and/or reduce the volume of the reactor thereby reducing the cost of protein extraction. Therefore, a 1 h reaction time for protein extraction is recommended. The results showed that the combined fish waste can be used for protein extraction without any segregation.

Microalgae Oil Extraction Pre-treatment Methods: Critical Review andComparative Analysis

Microalgae biomass can be used to produce numerous value added products such as biodiesel, bioethanol, biogas, biohydrogen, fish feed, animal feed, human food supplements and skin care products. Production of value added products from microalgae biomass requires the growth and recovery of the algae biomass, extraction and downstream processing of the desired product. One of the major obstacles for using microalgae biomass on an industrial-scale, for the production of biodiesel, is the high processing costs. Increasing the lipid recovery efficiency from the microalgae biomass would result in greater product yields (biodiesel). Thus, the aim of this study was to review the current methods used for microalgae pre-treatment and perform a comparative analysis in order to determine the most economically efficient method for large scale use. The effectiveness of the pre-treatment methods investigated was evaluated based on: (a) cell wall disruption efficiency, (b) cost, (c) toxicity (d) suitability for large scale use, (e) time, (f) reusability and (g) maintenance. Different treatment methods included mechanical techniques (shaking vessel and agitated bead mills and horn and bath sonication), thermal methods (steam explosion, freeze drying and autoclave), electromagnetic radiation (microwave) and biological treatments (enzymatic). The results indicated that of the 9 microalgae methods investigated a mechanical, thermal and electromagnetic radiation techniques were suitable. These methods were bath sonication (81), steam explosion (93) and microwave radiation (87). Microwave assisted microalgae pre-treatment technique is rapid, effective in cell wall disruption, non-toxic, can be used for large volumes and the medium maybe reused, but it does however suffer from high maintenance costs. Bath sonication technique is effective in the degradation of cell wall, nontoxic, rapid technique with minimal maintenance required, but suffers from high costs and difficulty in scale up for industrial use. Steam explosion pre-treatment is effective in degrading microalgae cell wall, releasing intracellular components, rapid, reusable, relatively low in costs, environmentally friendly and reusable, but is species specific. Overall, the negative aspects of these three techniques are outweighed by their effectiveness, rapidness and relatively low costs when compared to other pre-treatment techniques. Other mechanical extraction methods suffer from high operational costs, lengthy treatment times, high maintenance costs and the scale up difficulty. Freeze drying and autoclave techniques were deemed unsuitable microalgae pre-treatment techniques because of the high costs, scale up difficulty and long processing times associated. Biological pre-treatment technique were deemed unsuitable as a result of high costs associated with purchasing of enzymes, difficulty in recovery/separation after treatment, long treatment time, and high maintenance required for high efficiency.

Effects of tetrazolium chloride concentration, O2, and cell age on dehydrogenase activity of Aspergillus niger

The effects of triphenyl tetrazolium chloride (TTC) concentration, cell age, and presence of O2 on the dehydrogenase activity of Aspergillus niger as measured by triphenyl formazan (TF) yield were investigated. The results indicated that increasing TTC concentration initially increased the TF yield and then decreased it. The maximum TF yield was observed at a TTC concentration of 30 g/L for young cells (4 d old) and 20 g/L for old cells (12 d old). Conducting the test under anaerobic conditions increased the TF yield. About 18% of the TF produced was converted back into TTC in the presence of oxygen. The relationship between dehydrogenase activity of A. niger (as measured by TF yield) and cell mass was found to be linear. A kinetic model describing the relationship between reaction rate (micromoles of TF formed per hour) and TTC concentration while accounting for substrate inhibition was developed, and the model constants were calculated. The optimum TTC-test conditions for dehydrogenase activity measurement of A. niger were a TTC concentration of 20 g/L, a pH of 9.0, a temperature of 55°C, an incubation time of 3 h, and anaerobic conditions.

Extraction of Chymotrypsin from Red Perch (Sebastes marinus) Intestine Using Reverse Micelles: Optimization of the Backward Extraction Step

Fish processing waste can be used to produce valuable by-products such as chymotrypsin which has applications in the food, leather, chemical and clinical industries. In this study, a reverse micelles system of AOT/isooctane was used to extract chymotrypsin from crude aqueous extract of red perch intestine. The effects of pH and KCl concentration of the backward extraction step on the total volume (TV), volume ratio (VR), total activity (TA), enzyme activity (AE), specific activity (SA), purification fold (PF), protein concentration (Cp) and recovery yield (RY) were studied. Changing the pH from 6.5 to 8.5 and the KCl concentration from 0.5 to 2.0 M during the backward extraction step had no effects on the TV or VR. Increasing the pH from 6.5 to 7.5 increased AE, SA, Cp, PF and RY by up to 47.06%, 30.0%, 27.0%, 26.9% and 18.47%, respectively but they all then declined with further increases in the pH. Similar trends were observed when the KCl concentration was increased from 0.5 to 1.5 M. The decreases in these parameters were due to the denaturation of protein under high pH. The highest AE, Cp and RY were achieved with pH 7.5 and 1.0 M KCl concentration while the highest SA and PF were achieved with pH 7.5 and 1.5 M KCl concentration. Addition of isobutyl alcohol in the backward extraction step increased the TV, AE, TA, Cp, SA, PF and RY by 13.6%, 336.4%, 342.6%, 81.1%, 146.4%, 146.2% and 345.8%, respectively. Alcohol reduced the interfacial resistance for the reverse micelles and, thus, destroyed the reverse micelles structure. The values of AE, TA, SA, PF and RY obtained with reverse micelles methods were much higher (2.3 fold) than those obtained with the ammonium sulphate method.

Changes in Cell Structure, Morphology and Activity of Streptomycesvenezuelae during the Growth, Shocking and Jadomycin ProductionStages

Streptomyces venezuelae have the ability to synthesize a group of novel benzoxazolophenanthridine antibiotics called jadomycin. The aim of the study was to investigate the changes in activity, cell structure and morphology of Streptomyces venezuelae while subjected to different environmental conditions during the growth, ethanol shocking, and jadomycin production stages. The activity of S. venezuelae was measured using the triphenyl tetrazolium chloride (TTC) technique while the microbial population was measured using the optical density and plate count techniques. Samples from each stage were viewed under the scanning electron microscope (SEM) and transmission electron microscope (TEM). The specific TF yield was calculated by dividing the TF yield by the number of cells. The specific TF yield remained constant at 2.44 x 10-8(μmol/CFU) during the growth period in nutrient rich medium and decreased to 0.25 x 10-8 μmol/CFU and 0.28 x 10-8 μmol/CFU during the acclimatization to the nutrient deprived-amino acid rich production medium and after shocking and then increased to 3.67 x 10-8 μmol/CFU during jadomycin production. The ethanol shock did not cause 100% of the cells to change their morphology. Remarkable changes were observed in the morphology and structure (cell diameter, vacuoles present and septation/sporulation) of S. venezuelae during the four consecutive stages (growth, acclimatization, shocking and jadomycin production). The elemental analysis provided information for verifying jadomycin B purity (97.86%). However, it was not possible to detect jadomycin B within cells. It is probable that jadomycin was produced outside the cells by extracellular enzymes as opposed to intracellularly by the uptake of isoleucine and glucose. The white pellets (cells), obtained by centrifugation of production medium, supports the idea that jadomycin B is produced outside the cells as jadomycin is highly coloured compound. It is also possible that the cells were highly efficient at excreting the secondary metabolites. These hypotheses need further investigation.

Inactivation of Botrytis cinerea during thermophilic composting of greenhouse tomato plant residues.

The effectiveness of in-vessel thermophilic composting on the inactivation of Botrytis cinerea was evaluated. The bioreactor operated on an infected mixture of tomato plant residues, wood shavings, and municipal solid compost (1∶1.5∶0.28). Tap water and urea were added to adjust the moisture content and C∶N ratio to 60% and 30∶1, respectively. Used cooking oil was added as a bioavailable carbon source to compensate for heat losses from the system and extend the thermophilic compositing stage. The controlled thermophilic composting process was successful in inactivating B. cinerea. During all experiments, the average reactor temperature increased gradually, reaching its peak after 31 h of operation. Temperatures in the range of 62.6–63.9°C were maintained during the thermophilic stage by the intermittent addition of used cooking oil. The results of the enzyme-linked immunosorbent assay test indicated that the initial concentration of B. cinerea in the compost samples (14.6 μg of dried mycelium/g of compost) was reduced to 12.9, 8.8, and 2.4 μg/g after 24, 48, and 72 h of thermophilic composting, respectively. Plating assay indicated that the mold was completely inactivated in samples after 48 h of thermophilic composting. No significant reduction in B. cinerea was observed during the transient phase (first 30 h of rising temperature) because the temperature reached the lethal level of 55°C after 23 h, thus allowing only 7 h of exposure to temperatures higher than 55°C during this phase. The relatively short time required for complete inactivation of B. cinerea was achieved by maintaining a constant high temperature and a uniform distribution of temperature and extending the duration of the thermophilic stage by the addition of the proper amount of bioavailable carbon (used cooking oil).

Partition of Pepsinogen from the Stomach of Red Perch (Sebastes marinus) by Aqueous Two Phase Systems: Effects of the Salt Type and Concentration

An important acidic protease, pepsin is synthesized and secreted in the gastric membrane in an inactive state called pepsinogen (PG) and has applications in the food and manufacturing industries, collagen extraction, gelatin extraction and in regulating digestibility. Fish processing waste can be used to produce commercially valuable byproducts such as pepsinogen. In the present study, the purification of pepsinogen from the stomach of red perch using aqueous two phase systems (ATPS) formed by polyethylene glycol (PEG) and salt at 4°C was optimized. The effects of salt type (MgSO4, (NH4)2SO4, Na3C6H5O7 and K2HPO4) and concentration (6, 7, 8, 9, 10, 11, 12, 13, 15, 17, 19%) on the partitioning of PG were studied and parameters including total volume (TV), volume ratio (VR), enzyme activity (AE), protein content (Cp), specific activity (SA), partition coefficient (Kp), purification fold (PF) and recovery yield (RY) were evaluated. Salt type and salt concentration had significant effects on each parameter. MgSO4, (NH4)2SO4, Na3C6H5O7 and K2HPO4 required different critical salt concentrations (9, 12, 12 and 10%, respectively) to form biphasic systems. TV and VR decreased with increased salt concentration since salt formed hydrogen bonds with water molecules and created a more compact and ordered water structure. AE, CP, SA, PF and RY showed a maximum increase with intermediate salt concentration, while KP had the opposite pattern. The highest TV and AE values were obtained at 12% (NH4)2SO4 while the highest SA and PF values were obtained at 12% MgSO4. The highest TV and Cp values were obtained at 12 and 15% Na3C6H5O7, respectively. (NH4)2SO4 at 15% concentration gave the highest RY (71.7%) and was selected as the optimum salt type and concentration. Thus, 15% (NH4)2SO4 18% PEG 1500 was the optimal ATPS combination and presented the best partition. The values of SA and PF and RY obtained with ATPS method were two fold higher than those obtained with the ammonium sulphate fractionation (ASF) method.

Solid State Deproteinization of Shrimp Shells by Aspergillus niger with Galactose as a Bioavailable Carbon Supplement

The aim of the research was to evaluate the ability of the fungus Aspergillus niger to produce protease and carry out the deproteinization of shrimp shells and study the effect of adding galactose as an external carbon source at three concentrations (10, 20 and 30% w/w) on the performance of the deproteinization process. The results showed that the 20% galactose concentration was optimum whereas the 10% galactose concentration did not support enough microbial growth and the 30% galactose concentration inhibited the growth of A. niger as was evident from the temperature and carbon dioxide evolution profiles. The temperatures of the shrimp shells and exhaust gas decreased in the first 12 hours (lag) because the heat losses due to evaporation of water (latent heat) and the cooling effect of the inlet air were higher than the heat generation by microorganisms. It then increased as a result of heat accumulation in the bioreactor reaching 28.9- 38.3 and 24.9- 29.0°C, respectively. There was a strong correlation between the concentrations of carbon dioxide in the exhaust gas and the temperature of the shrimp shells. Although the inlet air was humidified, a significant reduction in the moisture content (from 60% to 25.20–43.71%) was noticed by the end of the deproteinization process because the moisture lost through evaporation exceeded the metabolic water production. The pH of the shrimp shells decreased with time to 5.92–6.63 due to acid protease production and then increased to 6.28–8.32 due to the buffering capacity of the calcium carbonate released from the shrimp shells. The protease activity increased from 0.71 U/g to 1.77–1.85 U/g whereas the protein concentration in the shrimp shells decreased from 30.84% to 20.77-25.30 % as a result of protein break down by the proteolytic enzymes produced by A. niger. The chitin concentration in the shrimp shells increased from 16.59% to 20.42-21.99% as a result of protein removal. The highest protease activities, protein removal efficiency and chitin concentration were achieved with galactose concentration of 20%. The spent shrimp shells from the runs that received 10 and 20% galactose concentration had a pale pink-orange color. The existence of the pink-orange color was an indication of the presence of pigments which were not utilized during the fermentation process. The run that received 30% galactose concentration had a gray-black color due to the presence of A. niger spores. The high initial galactose concentration enhanced sporulation of the fungus.