هانیه شکرکار

Chlorophyll and carotenoids can be extracted from microalgae using different solvents. In this study, for the first time, the extraction yield of pigments from mixed microalgae was compared in wet and dry conditions. The extraction yield of chlorophyll a, b and carotenoid using acetone solvent (without stirring) from wet algae equal 21.83%, 78.12%, and 66.01% respectively and from dry algae equals 61.34%,57.19%, and 53.27%, respectively. Then, to select the suitable solvent, acetone, ethanol, methanol, dimethyl ether, and tween (20% and 85% ) as non-ionic surfactants were used. Due to the difficult storage conditions of wet algae, dry algae was used in these experiments. The results show that the highest extraction yield of chlorophyll a, b, and carotenoid using tween (85%) without stirring on the tenth day is 91.70%, 87.12%, and 79.9% respectively. Also, the extraction yield with methanol solvent after 10 hours was 82.70%, 65.12%, and 62.90%. To reduce the extraction time using tween (85%), stirring was used. According to the results, the use of stirring increases the extraction rate of pigments, so that the extraction yield reached 98% within 50 min.

Microalgae biomass is considered as a sustainable feed for the production of high value compounds such as enzymatic and non-enzymatic antioxidants that are widely used in food, pharmaceutical, textile, leather as well as in the chemical industry. Increasing the yield of microalgae, achieving optimal culture conditions, optimal storage of antioxidant molecules after processing and downstream processing with energy saving are among the main obstacles to the production of antioxidants. Today, antioxidant compounds produced by microalgae as a result of stressful conditions, as important products in the field of human health, have received commercial attention. Oxidative stress due to acidity, metals, UV and temperature can cause the production of antioxidants in many different species of microalgae such as Dunaliella algae. Dunaliella algae cultivation has several advantages, including high growth rate, low production cost, as well as the ability to grow in stressful conditions such as high salt concentrations, high light intensity, and nitrogen restriction. This article provides an overview of the production of antioxidants in the Dunaliella microalgae cellular metabolism, the activity of antioxidant enzymes (POD, SOD, CAT) and strategies to increase antioxidant accumulation in microalgae.

Chlorophyll and carotenoids are essential compounds in many everyday products. These substances are used not only as an additive in pharmaceutical and health products but also as a natural food coloring. In addition, they have antioxidant and anti-mutagenic properties. Extraction of these compounds is based on cell degradation methods and the chemical solubility of the compounds. Methods of separation of these compounds include chromatographic, solvent, supercritical, enzymatic, ultrasound, and microwave methods. One of the most important issues related to the extraction of chlorophyll and carotenoids from microalgae in the culture medium is the need for an efficient, cost-effective, and high-yield extraction process. The greatest limitation in the biological processing of pigments is related to the installation of equipment and operation. Therefore, the purpose of this study is to investigate the main methods for the extraction of chlorophyll and carotenoids from microalgae by considering the advantages and disadvantages of each method.

In this study, the effect of the electrocoagulation process on the performance of the membrane bioreactor system was investigated using a laboratory setup and synthetic wastewater. First, the reactor without electric current, then in four different modes including anode and cathode (Al), the distance between anode and cathode (3.5, 2.5 cm), electric field (2.5, 1.5 Volts), and continuous or alternating current applications (one min on, 4 min off) were evaluated. Recent research shows that all of these factors affect membrane flow flux, activated sludge properties, and soluble microbial products (SMP) and extracellular polymeric substances (EPS) concentrations. The results showed that for EMBR reactor (voltage 1.5 V, the distance between anode and cathode 2.5 cm and application of intermittent current (one min on, 4 min off), better performance in reducing membrane fouling, reducing SMP and EPS. So that the membrane fouling rate, EPS, and SMP were reduced by 57%, 59%, and 58%, respectively. Also, the COD removal was 75% for the MBR reactor and 99% for the EMBR.

Microalgae with reserves of carbohydrates, high growth rate have been introduced as one of the most promising sources for bioethanol production. In this study, after culturing mixed microalgae species in photobioreactors, a nitrogen starvation strategy was used to increase the accumulation of carbohydrates in microalgae. Then, the sugars in the biomass were extracted using enzymatic hydrolysis by cellulase enzyme. For the first time, the enzymatic hydrolysis of microalgae is investigated by considering the dynamic conditions of the fluid inside the reactor. The results showed that increasing the system agitation more than the enzyme concentration affects the hydrolysis efficiency. At high speeds of 250 rpm, where the flow regime changes from slow to turbulent, the amount of sugar released is much higher than the values at low speeds of the stirrer. Also, adding baffle increases the mass transfer rate by preventing the formation of vortices and consequently increases the hydrolysis efficiency. But changingthe type of stirrer does not have a significant effect onthe hydrolysis process. Also in this study, the effect of agitation during the hydrolysis process was investigated by evaluating the mass transfer rate.

Sanitary disposal is one of the waste disposal methods, which contains a lot of harmful effects especially air pollution. As a result of the biodegradation process, pollutant gas contains Biogas, Methane, Carbon Dioxide, produced from landfills within which, Methane gas has a huge effect on air pollution in comparison to other gases. In this paper, seven cities of Iran, including Tabriz, Tehran, Shiraz, Bandar Abbas, Khoy, Astara, and Mashhad have been studied for the simulation of pollutant gas emissions according to various climatic conditions in them. After collecting population growth rate, type of landfill area, and the average lifetime of the displacement site pollutant Emissions from Landfills were simulated by using LandGEM software. The findings of this study demonstrate that the highest methane production rate among the studied cities, due to the humid and normal weather for Astara and the dry weather for other cities will occur in 1415 (2036) in Tehran. Using the results obtained from this study, it is possible to design methane gas collection systems for each site. therefore, in addition to the use of pollutant gases, its accumulation in the landfill site and the explosion probabilities are also prevented.

Microalgae are promising sources of protein due to their high nutritional value, rapid growth rate and ability to survive in harsh conditions. In this study, first, different and indeterminate species of microalgae were cultured in flat plate photobioreactors and for the first time, the process of protein extraction from mixed microalgae biomass using various pretreatment methods such as autolysis, hydrolysis with acidic and alkaline methods, ultrasound and their composition was investigated. In acidic and alkaline pretreatment using solutions with different concentrations and at different times, the highest percentage of protein extraction (at 121 temperature and duration of 30 minutes) was 83% and 93%, respectively, which showed that the use of alkali was more efficient in protein extraction. Also, using autolysis and ultrasound methods, the highest extraction efficiencies were 60% and 39% of total protein, respectively. In this study, an autolysis with freezing method was used for the first time and based on the results, the efficiency of the autolysis process increased by 3 to 10%.

​Microalgae with stores of carbohydrates are introduced as a promising energy resource to produce In this study, a mixed culture was used for reducing the processing costs. Afterward, nitrogen starvation strategy was used to increase the storage in The application of mixed cultures enhances the economic feasibility of the process due to the elimination of culture sterilization. After harvesting and drying enzymatic hydrolysis of microalgal biomass for extraction Afterward, the enzymatic hydrolysate of microalgal biomass (25, 50, 100g/L) underwent fermentation with Saccharomyces cerevisiae and kinetic models for fermentation were studied. The inhibition of glucose substrate and product was considered in the kinetic model. AQUASIM 2.0 software was used as a tool to simulate the fermentation process. The estimated values of the maximum specific growth rate (μ) Monod constant (Ks) to be 0.281h −1 1.8g/L, respectively. Also, the results indicate that the kinetic model predicted the behavior of the system well.

Some key factors such as high growth rate, low demand for arable land and fresh water and high carbohydrate content causes microalgae to introduce a new sourceof bioethanol.In this study,mixed microalgae culture was cultivated in the plate photo-reactors. Afterwards, nitrogen starvation strategy was used to accumulate storage carbohydrates. After harvesting of microalgae, enzymatic hydrolysis was applied to extract the sugars in biomass. The concentrations of extracted reducing sugar using hydrolysis process were investigated at four different substrate concentrations and three different temperatures over time. The process simulation by neural networks was performed using MATLAB software program. The networkinput consisted of substrate concentration, temperature, hydrolysis time and the networkoutput consisted of reducing sugar concentration. Artificial neural network with one hidden layer of 8 neurons in conditions (70-15-15) has minimum Mean Square Error (MSE).

In this paper, results of the oily wastewater treatment by ceramic membranes in microfiltration process are simulated using neural network and hermia model. The process simulation by neural networks is written using MATLAB software program. The network input consisted of oil concentration (Coil), cross-flow velocity (CFV), temperature (T), trans-membrane pressure (TMP), and filtration time (t) and the network output consisted of permeation flux. The operational data is divided in three categories: training, validation and testing. In this study, three modes (20-20-60 and 15-15-70 and 10-10-80) are investigated for training the network. Also formation of precipitate is modeled using hermia model includes four different behavior in obstruction. In all states are observed prediction of permeation flux using neural network is better than hermia model.

Due to extensive usage of microfiltration membranes in industrial –scale, modeling of this processes are important and imperative. MF is one of the processes which are used for certain types of separation. In this paper, treatment of oily wastewaters with ceramic MF membranes was studied and a new approach has been suggested for modeling the concentration polarization layer in the waste water membrane system. Effects of various operation conditions (trans-membrane pressure (TMP), cross-flow velocity (CFV), temperature (T), oil concentration (C), and filtration time (t)) on the concentration profile and polarization layer are studied. A numerical solution of advection–diffusion equation has been developed using a control volume approach based on the finite element method. As will be observed, model behavior complies well with anticipations.