الفهرس 
Literature ReviewOnly 14 pages are availabe for public view
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Abstract
The world has recently moved to non-traditional sources of energy to search for a new source that has the capacity to bridge the widening gap between the size of the available and the size of the consumer of energy sources without negatively affecting the balance of environmental components. This work falls under the banner of one of these attempts or what they call it the third generation of bioenergy. Petroleum fuels (gasoline or diesel oil) used in various fields can be replaced with bio-fuel sources such as bioethanol and biodiesel. These vital and renewable sources do not cause sulfur, greenhouse gas and/or particulate matter emissions and do not contain heavy metals such as lead, thus improve and maintain the environmental conditions.
The microalgae, or macroalgae, are a good and promising source of clean biofuels, which falls under the third generation biofuels. Due to what has been observed through previous studies, this study has been directed initially at the search for the highest microalgal lipid content that can be extracted and converted by chemical treatments into biodiesel to replace diesel as a petroleum fuel, as well as, the search for macroalgae that have the highest carbohydrate content that can be converted by chemical and biological treatments into bioethanol to replace gasoline as petroleum fuel.
In this context the present study has been divided into two parts. The first part, which deals with macroalgae of the three different types (brown, green and red), which were collected from three different locations in Egypt, one location at Red Sea Governorate including the brown Sarragasum sp. and two locations at Alexandria Governorate including the green Ulva sp. and the red Jania sp.. Three different treatments have been tested for that biomass to obtain the highest total reducing sugars (TRS) for the production of bioethanol: (1) Thermo-chemical hydrolysis using different concentrations of H2SO4, HCl and NaOH (2) Hydrothermal hydrolysis of algal biomass followed by fungal saccharification at different incubation periods (3) Thermo-chemical hydrolysis of biomass using the best acid concentration (HCl 1%), followed by fungal saccharification.
The results showed that the best treatment of macroalgal biomass was No. 2, where the highest percentage of total reducing sugars which could be converted into bioethanol was (182 mg TRS /g biomass) and obtained when Trichoderma asperellum RM1 was used in the hydrolysis of the biomass of Sargassum latifolium. The results showed also that the combined use of two Saccharomyces strains had the best effect, a higher percentage of ethanol was obtained from the total reducing sugars (0.29 g bioethanol/ g initial TRS) compared to Saccharomyces cerevisiae ATTC 76621 (0.11 g bioethanol/g initial TRS) or Saccharomyces cerevisiae strain RM2 (0.06 g bioethanol/ g initial TRS), respectively.
The second part of the current study deals with microalgae, as follows:
(1) Collection of different saline samples from six different sites; 2 sites at the Red Sea Governorate (General Petroleum Company R1; where the samples are contaminated with crude oil + West Bakr beach R2); and 4 sites at Alexandria Governorate (Abu Qir beach A1 + Shatibi beach A2 + National River Ports Management Company A3 + El-Mex Salinas Company A4).
(2) Physico-chemical analysis of the collected water samples was done to identify the composition of the natural environment from which the algae were isolated.
(3) Enrichment of microalgae has been done on four different culture media (F/2 medium, Johnson’s medium, Zarrouk’s medium and BG11 medium), and as a result four pure isolates were obtained (Tetraselmis sp. RM2, Stichococcus sp. RM3, Nannochloris sp. RM4 and Dunaliella sp. RM5). The lipid content of each isolate was measured at different time intervals in order to select the best in terms of the increase in biomass, as well as, the increase in lipid content, by differentiation between the results of biomass and lipid contents of the four isolates it has been found that the best isolate was Nannochloris sp. RM4 and therefore it was selected for further research.
(4) The polycyclic aromatic hydrocarbon, pyrene, was used to study its effect on the four isolates as one of the petroleum contaminants at a concentration of 100 mg/L. It has been found that Tetraselmis sp. RM2 showed the best phycodegradation percent (25%) after 25d of incubation and the resulting biodegradation metabolites were also identified using HPLC to elucidate the metabolic degradation pathway of pyrene after colorimetric detection of a catechol-1,2-dioxygenase enzyme involved in that pathway to be sure of the complete mineralization of such contaminant.
(5) After that, the study of the factors that positively affect the increase of the lipid content of Nannochloris sp. RM4 has been performed in the following steps:
(a) Organic and in-organic change in the chemical composition of the culture medium used for the growth of Nannochloris sp. RM4, such as the use of corn steep liquor (CSL) as a carbon source at different concentrations (0.5, 1.0, 2.0, 5.0, 7.0 g/L), and the use of different nitrogen/phosphorus (N/P) concentrations (0.15:0.004; 0.18:0.005; 0.375:0.01; 0.75:0.02; 1.5:0.04 and 3.0:0.08). The decrease in lipid content of Nannochloris sp. RM4 was observed with the increased concentration of CSL, while the lipid content increased to its maximum (30.4%) when the concentration of CSL was ( 0.5 g/L) after 19 days of incubation. On the other hand, the lipid content of algae was gradually increased with the increase of nitrogen/phosphorus (N/P) concentration up to (0.375: 0.01), reaching (30.3%) after 19 days of incubation and decreased at higher concentrations.
(b) Different light/dark periods (16:8, Light: dark), (14:10, Light: dark) and (12:12, Light: dark). The decrease in lipid content of algae was observed gradually with the decrease in light hours, reaching a maximum (30.1%) at (16:8, Light: dark) after 19 days of incubation.
(c) Different concentrations of sodium chloride NaCl (20, 25, 30, 35 and 40 g/L). The lipid content was increased to a maximum (30.4%) at the concentration of (25 g/L) after 19 days of incubation.
(d) Different culture volume effect (i.e. the effect of upscaling) through comparison of the production of total lipids of Nannochloris sp. RM4 under the previous optimal conditions by using (20L working volume) photobioreactor and (100 mL working volume) small size culture flask to study the effect of working volume as one of the factors influencing the production of biodiesel on the industrial level. There was no significant difference between the two cultures; the lipid concentration and dry biomass obtained by using 20L photobioreactor were (5.9 and 20.8 g/L) and by using small size culture flask they were (6.3 and 21.1 g/L), respectively, after 19 days of incubation.
At the end of this part, the resulting lipid content was converted to biodiesel chemically and the resulting fuel was analyzed and evaluated. Analysis of the fatty acid profile of biodiesel was studied using gas chromatography. The results showed that it contains the following fatty acids at varying degrees: lauric acid, myristic acid, palmetoleic acid, heptadecanoic acid, stearic acid, linoleic acid, linolenic acid, eicosenoic acid. Palmitic (33.2%) and oleic acids (26.3%) were the highest fatty acids in the biodiesel. In order to evaluate the biodiesel as an alternative fuel, some important properties were identified that affect its use as fuel such as the density, kinematic viscosity, pour point, flash point, cetane number and calorific value; which were evaluated on the basis of their comparison with the standards of Egyptian diesel and international biodiesel standards. The results showed that all the characteristics of biodiesel produced are acceptable and meet most specifications, use as an alternative and/or supplement to diesel oil. Moreover, the spent biomass after lipid extraction can be used for; (1) pigments production ( chlorophyll a, b and carotenes) as natural colouring and therapeutics; (2) carbohydrates for bioethanol production; (3) it can be used as animal food supplements and/or animal fooder; (4) Not only this but also the spent waste algal biomass can be used as a solid biofuel or for production of biogas.