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In biological engineering, cell immobilization is a modern technique for immobilizing free cells in a small space. Disintegration and elimination of azo dyes [Reactive Orange 122 (orange 2RL) and Reactive Red 194 (Reactive Red M-2BF)] were investigated by using

The third-generation bioethanol production depends on the utilization of algae as raw material and an excellent source of polysaccharides, which can be fermented to bioethanol. The microalga Chlorella vulgaris is suitable for bioethanol production due to its carbohydrate content. In this study, the chemical pretreatments of acidic and alkaline pretreatments of Chlorella vulgaris biomass showed that the maximum reducing sugars and total carbohydrate concentrations produced from acidic pretreatment of the algal biomass by using 2% sulfuric acid (H2SO4) at 120 °C for 30 min were (24.77 g/100 g dried biomass) and (16.08 g/100 g dried biomass), respectively. The bioethanol released from the biomass was increased gradually until the 5th day (14.32 g/100 g dried biomass). The maximum bioethanol produced after 2% (w/v) of sodium hydroxide (NaOH) at 120 °C for 30 min. alkaline pretreatment was (21.54 g/100 g dried biomass) reducing sugar, (15.72 g/100 g dried biomass) total carbohydrate and the produced bioethanol concentration on the 4th day (7.74 g/100 g dried biomass). At the same time, the physical pretreatments were done by microwaves and ultrasonication. The highest reducing sugars after ultrasonication, (18.97 g/100 g dried biomass) which fermented to (16.19 g/100 g dried biomass) bioethanol at the 4th fermentation day. While microwaves pretreatment reached (11.22 g/ 100 g dried biomass) reducing sugars, that synthesis (2.91 g/100 g dried biomass) at the 5th fermentation day. This work concluded that 2% H2SO4 was the best treatment method, which resulted in the highest concentrations of reducing sugars, total carbohydrate, and bioethanol.

Synthetic dyes are scattered in untreated or inappropriately treated effluents, and their dangerous items created during the halfway corruption are released into the water bodies that cause a horrendous smell, which prompts anomalous changes in the nature of water. In the present study, green algae and cyanobacteria are considered as a significant hotspot for decolorizing color and material gushing. Chlorococcum sp., Scenedesmus obliquus, Chlorella vulgaris, and Oscillatoria sp. were investigated for degradation and removal of some azo dyes [Reactive Orange 122 (Orange 2RL) and Reactive Red 194 (Reactive Red M-2BF)]. The results showed that the maximum decolorization was spotted at 20 ppm Reactive Orange 122 with Oscillatoria sp. mixed with S. obliquus (98.54%). 20 ppm Reactive Red 194 was decolorized by Oscillatoria sp. mixed with S. obliquus (97.58%) after 7 days of incubation. The decolorization was detected by spectroscopic analysis and Fourier transformed infrared (FTIR) spectroscopy. The suitable factors that accelerated the azo dye decolorization and enhanced the biological treatment methods to be more effective and speedier in decolorization were investigated. At 25 °C and continuous lighting, the highest percentage of the azo dye decolorization was obtained; BG11 was the suitable medium that gives a high percentage of the azo dye decolorization. However, relative to the effect pH on azo dye decolorization, results show pH 11 and pH 9 more effective on azo dye decolorization for Reactive Orange 122 and Reactive Red 194, respectively. A total of 6% of thiamine and ascorbic acid recorded maximum degradation activity at Reactive Orange 122 when treated with Oscillatoria sp. mixed with S. obliquus 79.13% and 77.18%, respectively.

Microalgae are a diverse group of microorganisms, the majority of which are photosynthetic in nature. Microalgae have different applications, the most important of which is the biological treatment of wastewater. Microalgae grow in various types of wastewater, such as wastewater polluted by Azo dyes, due to microalgae using wastewater as a culture medium, which contains many nutrients like nitrogen, phosphate, and carbon sources. Microalgae grow in various types of wastewater, such as wastewater polluted by Azo dyes, due to microalgae using wastewater as a culture medium, which contains many nutrients like nitrogen, phosphate, and carbon sources. So, microalgae are used for bioremediation of wastewater due to the efficiency of growing in wastewater and for the high production of lipids followed by trans-esterification to biodiesel. Face-centered central composite design (FCCCD) was used to determine the factors that have the most significant impact on the simultaneous decolorization of methyl red and lipid production by the fresh green alga Scenedesmus obliquus. The predicted results indicated that the alga decolorized 70.15% methyl red and produced 20.91% lipids by using 1 g/L nitrogen, an incubation time of 10 days, a pH of 8, and the concentration of methyl red is 17.65 mg/L. The dry biomasses of S. obliquus were also examined by SEM and FTIR before and after treatment with methyl red. SEM and FTIR showed that the properties of dry S. obliquus were altered after the biosorption of methyl red. According to GC-MS analysis of hexane extracts of S. obliquus, the lipid profile differed before and after methyl red decolorization. The results proved that it is possible to use S. obliquus to remove dyes and produce renewable fuels such as biodiesel. The novelty of this study is that this is the first time in which the effect of nitrogen concentrations in the medium used for algal growth on the removal of dye has been studied.

Biosorption by algae is an effective process for the removal of heavy metals from the aqueous solutions. The present work deals with the biosorption of Cd(II) by Chlorella vulgaris in a batch system. The biosorption efficiency of Cd(II) removal was studied at different pH (3–8), initial metal concentrations (20–100 ppm), agitation time (5–120 min.), agitation speed (50–250 rpm), and biomass dosage (0.01–0.1 g/50 ml of metal solution). The optimum conditions for maximum biosorption capacity for C. vulgaris were at pH 6, initial Cd(II) concentration 75 mg/l, biomass dosage 0.08 g/50 ml metal solution, temperature 25 °C, agitation speed 250 rpm, and agitation time 30 min. The cadmium removal efficiency of the raw and pretreated algal biomass was studied under the optimum conditions. The results showed that pretreatment with acetic acid gave 99.346% as compared with raw biomass. Different algal weights (0.2, 0.15, 0.1, 0.05, and 0.025 g) were immobilized with 10 ml of 4% calcium alginate. The results showed that the highest cadmium biosorption efficiency was 76.448% for 0.025 g as compared with the control. The biosorption mechanisms were examined by Fourier-transform infrared analysis and scanning electron microscopy for raw and pretreated algal biomasses before and after cadmium biosorption. It was found that hydroxyl, amide with hydrogen bond, and carbonyl stretching in carboxyl groups played an important role in biosorption.

A S A RESULT of its wide usage in the textile and other industries, dyes are widely detected in industrial wastewater. Algae and cyanobacteria can degrade and mineralize a number of dyes, presuming that the reduction appears to be related to the molecular structure of the dyes and the algal species used. The present study was conducted to investigate the potential of the green alga Chlorella vulgaris and the Cyanobacterium Aphanocapsa elachista isolated from polluted industrial regions for biodegradation of some pollutant dyes. The dyes used in this investigation were Disp orange 2RL, Reactive yellow 3RN, Reactive Black NN and Tracid Red BS. The results revealed that the maximum decolorization was observed in Disp. Orange 2RL (Azo dye) by Chlorella vulgaris (55.22%) after 7 days of incubation, while, Aphanocapsa elachista decolorized reactive yellow 3 RN (Azo dye) by 49.16%. Azo reductase enzyme in the used alga is responsible for degradation of azo dyes into an aromatic amine by cleaving the azo linkage. The results showed that treatment of Chlorella vulgaris with Disp Orange 2RL induced the azoreductase enzyme by 62.17% and Aphanocapsa elachista with Reactive yellow 3RN by 52.48% after 7 days of incubation. After decolorization, the degradation products were identified and confirmed by spectroscopic analysis (FTIR, GC/MS). This work concludes the ability of some microalgae and cyanobacteria for biodegradation of environmental pollutants.

The ability of Chlorella vulgaris, Lyngbya lagerlerimi, Nostoc lincki, Oscillatoria rubescens, Elkatothrix viridis and Volvox aureus to decolorize and remove methyl red, orange II, G-Red (FN-3G), basic cationic, and basic fuchsin was investigated. These algae showed different efficiency for colour removal; varied from ∼4 to 95% according to the algal species, its growth state and the dye molecular structure. Basic cationic and basic fuchsin were the most susceptible dyes for decolorisation and removal by all algae being tested, and up to ∼82% of methyl red was also removed by N. lincki and O. rubescens. However, the algal activity to decolorize orange II and G-Red was markedly fluctuated and lower. C. vulgaris displayed activity to remove ∼43.7 and 59.12% while as V. aureus removed 5.02 and 3.25% of the added dyes respectively. The results also showed that treatment of either C. vulgaris or N. Linckia with G-Red or methyl red, respectively, induced the algal azo dye reductase enzyme by 72 and 71% at the same order.

The processes of biodegradation have widely used to remove hazardous material from aquatic and soil system is an environmental friendly tool. The present study was conducted to investigate the decolorization and biodegradation of some dyes using some microalgal species isolated from pollutant industrial regions. Two microalgal species (cyanobacteria) were isolated and were identified as Pseudo anabaena sp. and Microcystis aeruginosa. The ability of the two algae to remove and decolorize Disp.orange 2RL, reactive yellow 3RN, Reactive black NN and Tracid red BS were investigated. The results revealed that the removal of these dyes depends on the algal species, its growth rate and the structure of dyes. The maximum decolorization was observed in Reactive black NN and Disp.orange 2RL by M. aeruginosa 55.12 % and 65.07 %, respectively after 7 days incubation. Also Pseudo anabaena sp. decolorized Reactive yellow 3RN and Tracid red BS by 58.47 % and 78.44%, respectively. Azo reductase enzyme of algae which responsible for degradation of azo dyes into aromatic amine by cleavage the azo linkage was estimated. The results showed that treatment of M. aeruginosa with Disp.orange 2RL induced the azo reductase enzyme by 68.04% and Pseudo anabaena sp. with Reactive yellow 3RN by 55.64 % after 7 days of incubation. The degradation product after decolorization was examined by spectroscopic analysis and Fourier transformed infrared spectroscopy analysis.

In this work, the oxidation of phenolic compounds was accompanied by shift in the wavelength and change in the colour such as the oxidation of phenol to catechol by Volvox aureus, Nostoc Linckia and Oscillatoria rubescens . The oxidation of β-naphthol by Volvox aureus, Lyngbya lagerlerimi and Nostoc linckia , and the oxidation of catechol by Chlorella vulgaris and V. aureus were suggested. The degradation of polycyclic aromatic hydrocarbons by different algae seems to be related to the molecular structures of the compound and physiological metabolism of the algae. The highest percentage of degradation of naphthalene by N. linckia after 7 days was 47.71%, while the highest percentage of degradation of anthracene by E. viridis after 7 days was 92.28%. The highest percentage of degradation of 2-methythie 3-phenyl quinazlin-4- 3H (one) by V. aureus after 7 days was 83.39%, and the highest percentage of degradation of 2- phenyl 3,1benzexazin-4 one by E. viridis after 7 days was 79.74%. The obtained results suggest that microbial biodegradation of pollutants can be used to clean up contaminated environments. Biotreatment of wastes using living organisms is an environmentally friendly, relatively simple and cost-effective alternative to physico-chemical processes.