Giorgos Markou

• Ph.D.
• Researcher at National Agricultural Research Foundation

Aquatic organisms, such as microalgae (Chlorella, Arthrospira (Spirulina), Tetrasselmis, Dunalliela etc.) and duck-weed (Lemna spp., Wolffia spp. etc.) are a potential source for the production of protein-rich biomass and for numerous other high-value compounds (fatty acids, pigments, vitamins etc.). Their cultivation using agro-industrial wastes a...

Nitrogen (N) limitation is considered as the most efficient strategy to induce the accumulation of lipids, carbohydrates or other target compounds in microalgal biomass. However, along with biomass biochemical composition, alterations in N limitation affect the photosynthetic apparatus and result in decreased growth. In this study, Chlorella vulgar...

Microalgae and cyanobacteria are a promising new source of biomass that may complement agricultural crops to meet the increasing global demand for food, feed, biofuels and chemical production. Microalgae and cyanobacteria cultivation does not interfere directly with food production, but care should be taken to avoid indirect competition for nutrien...

This study investigates the production of high-purity cellulose pulp from peach (Prunus persica) fruit wastes generated during the processing of a Greek compote and juice production industry. A three-step chemical process is used, including alkaline treatment with NaOH, organic acid (acetic and formic) treatment, and hydrogen peroxide treatment, wi...

Nannochloris sp. JB17 has been identified as an interesting microalgal species that can tolerate high salinity and high bicarbonate concentrations. In this study, Nannochloris sp. JB17 was long-term adapted to increased bicarbonate concentrations (10–60 g NaHCO3 per L) in fresh or sea-water-based growing media. This study aimed to evaluate its grow...

Cheese whey (CW), a byproduct resulting from dairy processing, requires proper treatment and disposal. The use of microalgae during tertiary treatment emerges as a promising option due to its efficiency to remove chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) from effluents obtained after secondary treatment processes....

Present study concerns the transformation of the agro-industrial by-products olive mill stone waste (OMSW) and walnut shell (WS) to a protein-enriched animal feedstuff utilizing the solid state fermentation (SSF) technique. For this purpose, various mixtures of these by-products were exploited as substrates of the SSF process which was initiated by...

Solid-State fermentation (SSF) is a valuable process used for the enhancement of the nutritional profile of agro-industrial by-products. The main objective of the present study concerns the exploitation of a mixture consisting of Cottonseed Cake (CSC) and Lathyrus clymenum pericarp (LCP) at a ratio of 80–20% w/w, which was utilized as substrate for...

Spirulina is a microalga recognized for its nutritional benefits and its potential in sustainable food production. Existing large-scale cultivation produces spirulina of very different quality, taste, and odor. The reason lies in various approaches to the production, which range from the low-technology simple systems to high-end high-quality produc...

Solid-state fermentation represents a sustainable approach for the conversion of agro-industrial wastes into high-added-value feed ingredients. The present study aimed to evaluate the effects of the dietary addition of a solid-state-fermented mixture of olive mill stone waste (OMSW) and Lathyrus clymenum husks (LP) on the antioxidant blood paramete...

This study aimed to examine the impact of crude glycerol as the main carbon source on the growth, cell morphology, and production of high-value-added metabolites of two microalgal species, namely Chlorella vulgaris and Scenedesmus quadricauda, under heterotrophic and mixotrophic conditions, using monochromatic illumination from light-emitting diode...

Biofloc technology (BFT) has gained increased interest as a potential low-cost and environmentally friendly method for sustainable aquaculture development. However, the addition of external organic carbon source and the increased aeration needed to promote biofloc formation could be a limitation of this technology. The integration of microalgae on...

Dear Professors and Researchers, I hope you are doing well. I am Guest Editor in the Special Issue: New insights in Wastewater Treatment by Microalgae and Fungi, in cooperation with Professors Abud and Markou. The Journal is Energy, Ecology and Environment (https://www.springer.com/journal/40974). The Issue is available in the Journal website (ht...

Microalgae have a high protein content (>40%), and their protein yield can be more than 10 times higher than that by conventional terrestrial crops (such as soya). Microalgal proteins display a well-balanced amino acid profile that meets FAO recommendations for human and animal nutrition requirements, and since they can provide all essential amino...

Arthrospira platensis is an edible cyanobacterium with high nutritional value. Even though A. platensis is not a marine species, it can be adapted to higher salinities, a strategy that could allow mass cultivation using brackish or saline water. In this work A. platensis was long-term adapted at different salinities (5–60 g/L NaCl added as natural...

The effects of spirulina consumption added in foods were investigated in two crossover clinical trials (n = 13 different healthy adults). In Trial-1 adults consumed cookies with-and-without spirulina (3.12 g per 100 g final product; 2.5 g spirulina per 50 g available carbohydrates) according to glycemic index (GI) methodology. In Trial-2, adults co...

Numerous studies have indicated that fruits and vegetables are considered as significant sources of bioactive compounds. The generated by-products, which are derived from the food industry, reveal similar or higher antioxidant activity. On the other hand, intense industrialization results in the production of large volumes of by-products, raising s...

The application of high-pressure technology (100–600 MPa, 20 °C for up to 20 min) for cell disruption and consequent extraction of proteins -including C-phycocyanin- from the cyanobacteria Arthrospira platensis (spirulina), was investigated. Wet spirulina biomass was suspended in three different aqueous systems (deionized water, phosphate buffer, 1...

Swine wastewater (SW) poses a great threat to the environment due to its high-nutrient profiles if not properly managed. Advanced biological treatment method is an efficient method to treat SW by screening potent microalgae or bacterial strains. In this study, activated sludge, three locally isolated heterotrophic nitrification bacteria and one mic...

The main objective of this study concerns the bioconversion of agro-industrial wastes into high added value products, such as proteinaceous animal feed, using Solid State Fermentation process (SSF). For this purpose, the Olive Mill Stone Waste (OMSW) which is known to contain low amounts of proteins and a high concentration of anti-nutritional subs...

Cultivation of photosynthetic microorganisms in wastewater is a potential cost-effective method of treating wastewater and simultaneously providing the essential nutrients for high-value biomass production. This study investigates the cultivation of the cyanobacterium Arthrospira platensis in non-diluted and non-pretreated brewery wastewater under...

Brewers’ spent grain (BSG) represents the 85% of the total residue produced during the beer brewing process, with a global annual production volume exceeding 30 Mtons. The current study concerns the application of solid state fermentation (SSF) as a bioprocess where the nutritional value of BSG is improved for further use as animal feed with increa...

As crude glycerol comprises a potential substrate for microalga fermentation and value added products’ biosynthesis, Auxenochlorella protothecoides was grown on it under heterotrophic and mixotrophic conditions and its growth kinetics were evaluated in a continuous system under steady state conditions. Increasing initial glycerol concentration (fro...

The main objective of this study concerns the bioconversion of industrial hemp extract residues (IHER) by applying a solid-state fermentation (SSF) bioprocess as a means to upgrade their nutritional composition, targeting their utilization as a proteinaceous animal feed. For this purpose, IHER underwent an SSF procedure initiated by P. ostreatus, a...

Biorefinery concepts that combine several valorization pathways, including both bioproducts and bioenergy/biofuels, are of high interest in order to maximize the economic value of microalgal cultivation systems. In this study, the residual biomass obtained from the microalga Chlorella vulgaris following the chemical extraction of a valuable fractio...

Dry anaerobic digestion (D-AD) generates nitrogen-rich effluents that are normally neglected in the circular bioeconomy. The high turbidity and ammonium content hamper nitrogen recovery from these effluents via biological processes, such as microalgae culture. The goal of this study was to demonstrate microalgae growth viability in high-strength D-...

The study herein concerns the application of the solid-state fermentation (SSF) bioprocess of agro-industrial wastes as a means to improve their nutritional composition, targeting their utilization as proteinaceous animal feed. The fermentation outcome resulted from the mixtures of Olive Mill Stone Waste (OMSW) with Pistachio Shell (PS) and PS with...

Varied cereal plants including, mushrooms, yeast, bacteria and algae are important sources of β-glucans, and many extraction procedures have been used in order to recover these valuable naturally occurring polysaccharides. The rheological and molecular properties of β-glucans can be utilized to be incorporated into various foods and to offer proper...

Background The enzyme alkaline phosphatase (ALP) is gaining interest because it exerts bioactive properties and may be a potentially important therapeutic agent for many disorders and diseases. Microalgae are considered an important novel source for the production of diverse bio-compounds and are gaining momentum as functional foods/feeds supplemen...

Featured Application Arthrospira (Spirulina) platensis enriched in β-glucans could be a potential ingredient for the preparation of novel functional foods. Abstract (1) Background: Arthrospira (commonly known as Spirulina) is an edible cyanobacterium that is produced worldwide as a food supplement owing to its high nutritional value. Arthrospira d...

This study examined the effects of monochromatic illumination (blue, red, green and yellow) employing light-emitting diodes (LEDs), trophic conditions (photoautotrophic and mixotrophic), and nitrogen availability (high and low peptone concentration) on the growth and biochemical composition of Auxenochlorella protothecoides. The results revealed th...

Brewers’ Spent Grain (BSG) represents the 85% of the total residue produced during the beer brewing process, with a global annual production volume exceeding the 30 Mtons. Study herein concerns the application of solid state fermentation (SSF) process for the efficient transformation of BSG into high nutritional value animal feed. The investigated...

Swine wastewater (SW) poses a great threat to the environment due to its high-nutrient profiles if not properly managed. Advanced biological treatment method is an efficient method to treat SW by screening potent microalgae or bacterial strains. In this study, activated sludge, nine locally isolated heterotrophic nitrification bacteria and one micr...

Microalgae (including cyanobacteria) have recently gained interest as a potential food and feed source due to their high nutritional value. Some microalgae and cyanobacteria have been traditionally consumed worldwide. Under the European Union’s legislation, they are considered, with only few exceptions, as novel foods, and therefore in order to ent...

Spirulina platensis, the most popular microalgae species known for its high protein content and bioactive compounds such as phycocyanin and allophycocyanin, has been studied for cheese fortification. Incorporation of spirulina in dairy products poses major sensorial challenges due to its characteristic odor and its insolubility in food formulation,...

The prevalence of functional foods has increased within the industrial production era. In this context, microalgae (including cyanobacteria) have become an innovative and promising resource of nutritional supplements as they are commercially cultivated to produce valuable compounds, including protein, pigments, lipids, essential amino acids, monoun...

Utilization of digestate as a source of nutrients must be understood in the context of their effects on light penetration. These conflicting consequences of digestate utilization were verified by growing the cyanobacterium Arthrospira platensis (Spirulina) in artificial seawater supplemented with 2.5%, 5%, 10% or 15% (v/v) of anaerobically digested...

Anaerobic Digestion (AD) is a process that is well-known and fast-developing in Europe. AD generates large amounts of digestate, especially in livestock-intensive areas. Digestate has potential environmental issues due to nutrients (such as nitrogen) lixiviation or volatilization. Using liquid digestate as a nutrient source for microalgae growth is...

Microalgae are photosynthetic aquatic microorganisms that fix CO2 and other inorganic elements into organic matter. In general terms, microalgae are considered as a very interesting source of biomass because of their great diversity on biochemical and physiological properties and their convenient agronomical characteristics, like high biomass yield...

In this study, the cyanobacterium Arthrospira platensis, commonly known as Spirulina, was cultivated utilizing phosphorus in the form of struvite recovered from effluents of a biogas plant treating municipal and agro-industrial wastes. Under the specific experimental conditions, providing sterilized struvite at about 120 mg/L (or 15 mg-P/L) gave th...

In this study, Arthrospira platensis was grown in the presence of different glycerol concentrations (0.5–9 g/L) under three light intensities (5, 10 and 15 Klux) in semi-continuous mode and under non-axenic conditions. The aim of this study was to investigate the growth performance, the biomass biochemical composition and any interactions between A...

Microalgae are a potential important source for the production of value compounds. Temperature constitutes an important factor for microalgae cultivation. Bioprocessing of microalgae in terms of optimization of the cultivation conditions could increase the production of some target compounds that are accumulated under stress conditions. Bioprocess...

Anaerobic digestion (AD) is a widely used technology for the treatment of organic wastes and by-products. Through AD, the organic matter is degraded producing a gaseous stream (biogas, which is a mixture of mainly methane and carbon dioxide) and a liquid/slurry stream (digestates) that contains most of the mineralized elements originating in the fe...

BACKGROUND The cyanobacterium Arthrospira contains proteins and the blue pigment phycocyanin that can be used as a natural colourant in the food industry. The aim of this study was to investigate a strategy for increasing the yield of phycocyanin and protein from Arthrospira cultures by shading the cultures with neutral density and red light filter...

In this chapter, the biological treatment process of wastewater and biomass, called anaerobic digestion, is discussed. It is a potential bioprocess to produce renewable energy as methane and hydrogen from underestimated and unexploited sources of organic matter. More specifically, this chapter will discuss the types of biodigesters utilized, the op...

Crude phycocyanin extract (PC-E) from a two-phase cultured Saharian Arthrospira sp. strain with a purity grade of 1.24 (reagent grade) was characterized regarding its stability, bio-functionality and bio-activity. PC-E showed higher solubility values above pH 6.0, while the maximum stability was achieved at pH 6.0. PC-E was stable only up to 50 °C,...

The interactive effects of light intensity, NaCl, nitrogen, and phosphorus on intracellular biomass content and extracellular polymeric substance production were assessed for Arthrospira sp. (Spirulina) in a two-phase culture process using principal component analysis and central composite face design. Under high light intensity (120 μmol photons m...

Research on biological processes for wastewater treatment (WWT) over the past decade has focused on the development of compact treatment processes at the expense of a high energy demand or a loss of valuable nutrients. The recent worldwide interest in the cultivation of microalgae for energy production, along with the need for more sustainable WWT...

Bioalcohols (mainly bioethanol) are considered as one of the most promising substitutes for fossil fuels. Several feedstocks have been evaluated as substrates for bioethanol production and among them, microalgae have particularly emerged during the past years. This is due to their rapid growth, lack of competition with crops, the integration of pro...

The performance of chemically pre-treated bentonite with Ca(OH)2 towards ortho-phosphate phosphorus (OPP) removal efficiency in synthetic (inorganic) and real (anaerobically digested effluents) wastewater (WW) was evaluated. The Ca(OH)2 pre-treated bentonite displayed a significant increase of OPP uptake (qe; mg P g–1 bentonite) of 40 and 15 times,...

Wastewater treatment technology with better energy efficiency and recyclability is in urgent demand. Photo-Sequencing batch reactor (SBR), which introduces microalgae into conventional SBR, is considered to have more potential for resource recycling. In this study, a photo-SBR was evaluated through the manipulation of several key operational parame...

Herein a techno-economic assessment was performed on an energy-crop based biogas plant coupled with a greenhouse for utilizing thermal energy produced by cogeneration. Seven energy crops were evaluated: triticale, maize, alfalfa, sunflower, clover, barley and wheat. According to the evaluation, triticale was the most competitive energy crop under s...

Phosphorus (P) recovery from wastewater is of great interest especially when the loaded adsorbent can be used in the agriculture as slow-release fertilizer. The application depends on environmental concerns related to the chemical modification of the adsorbent and the release of toxic compounds from the loaded material to the soil or the water duri...

In highly alkaline aqueous solutions (pH >10), the main form of dissolved ammoniacal nitrogen is the unionized free ammonia. Free ammonia being a gaseous molecule is easily striped out from the solution. Increasing wastewater pH is frequently used to force ammonia removal. Herein, the effect of the variation of some physico-chemical characteristics...

Spirulina cultivated on the low cost media

Bentonite was chemically pretreated with Ca(OH)2 to enhance orthophosphate phosphorus (OPP) sorption capacity (qe). The pretreatment resulted to an increase of qe from about 0.3 mg-P g-1 to about 8 mg-P g-1 at pH 7 and 25°C and OPP concentration 100 mg-P l-1. The effects of solution pH, OPP concentration, sorbent dosage, and temperature on OPP sorp...

The biosorption of phosphorus in the form of orthophosphate (Po) from wastewater using biomass as the sorbent is of potential importance because the Po-loaded biomass could be applied in the agricultural sector as fertilizer and soil conditioner. However, biomass generally displays a very low affinity for Po sorption and therefore biomass surface m...

In the present paper, the use of raw poultry litter (PL) as a nutrient source for the cultivation of Arthrospira platensis and Chlorella vulgaris was investigated. PL was added to acid solution (62.5 mM H2SO4) for the extraction of nutrients contained in PL. After settling, the supernatant, called PL leachate (PLL) was diluted 25 ×, 20 ×, 15 ×, and...

Flocculation of microalgae is a promising low-cost strategy to harvest microalgae for bulk biomass production. However, residual flocculants can interfere in further downstream processes or influence biomass quality. In this study, a new concept is demonstrated based on reversible magnesium hydroxide flocculation, using Chlorella vulgaris and Phaeo...

Herein a new approach of exploiting poultry litter (PL) is demonstrated. The suggested method includes drying of PL with simultaneously striping and recovery of ammonia, followed by the direct combustion of dried PL. The generated ash after the combustion, and the striped ammonia consequently, could be used as nutrient source for the cultivation of...

Poultry litter (PL) was pre-treated in order to reduce its nitrogen content and to increase the C/N ratio. The pre-treatment consisted of a first anaerobiosis phase of about 60days in order to accumulate ammonia nitrogen, followed by an ammonia stripping phase by heating the substrate at 80°C for 24h. The digestion was performed with PL and pre-tre...

A study was conducted to investigate the effect of light intensity (21, 42, and 63 μmol photons m(-2) s(-1)) and photoperiod (8:16, 12:12, and 16:8 h light/dark) on the biomass production and its biochemical composition (total carotenoids, chlorophyll a, phycoerythrin (PE), phycocyanin (PC) and allophycocyanin (APC), total protein, and carbohydrate...

In the present work the cyanobacterium Arthrospira platensis and the microalga Chlorella vulgaris were fed-batch cultivated in ammonia-rich wastewater derived from the anaerobic digestion of poultry litter. Aim of the study was to maximize the biomass production along with the nutrient removal aiming to wastewater treatment. Ammonia and phosphorus...

Comparing storability and the energy yield of biogas production from individual feedstock, energy crops perform better than most organic wastes such as manure and food waste and therefore in several European countries biogas is produced using energy crops. The most frequently used energy crop is maize silage. However, although maize has a high biom...

Production of microalgal biomass requires large amounts of nitrogen (N) and phosphorus (P). The sustainability and economic viability of microalgae pro- duction could be significantly improved if N and P are not supplied by synthetic fertilizers but with wastewater. Microalgae already play an important role in wastewater treatment, yet several chal...

In this study, zeolite was employed for the separation and recovery of P from synthetic wastewater and its use as phosphorus (P) source for the cultivation of the green microalga Chlorella vulgaris and the cyanobacterium Arthrospira (Spirulina) platensis. At P-loaded zeolite concentration of 0.15–1 g/L, in which P was limited, the two species displ...

This study is focused on copper and nickel biosorption onto Arthrospira platensis biomass of different biochemical compositions. Four types of A. platensis were employed, namely: (1) typical dry biomass (TDB), (2) carbohydrate-enriched dry biomass (CDB), (3) typical living biomass (TLB), and (4) carbohydrateenriched living biomass (CLB). The CDB wa...

In this study the combined effect of total ammoniacal nitrogen (TAN) concentration, initial biomass density and initial pH of the cultivation medium on growth of A. platensis was studied. The results indicate that TAN inhibition in relation to the initial biomass in unregulated pH cultures is neither a clearly biomass-independent nor biomass-depend...

In the present study, semi-continuous cultivation of Arthrospira platensis using various colors of light-emitting diodes (LEDs) as artificial lighting was performed in order to study their effects on the biomass composition of A. platensis. The lowest biomass productivity was obtained with blue LED (4.68 mg l(-1) day(-1)), while the highest was obt...

Herein a new approach for the application of wastewater nutrients for the cultivation of cyanobacteria or microalgae is described. Natural zeolite was used as medium for the sorption of ammonia from wastewater and subsequently as nitrogen releaser in cultures of Arthrospira platensis. The main scope of the present approach was to isolate ammonia fr...

In this study maize silage was anaerobically mono- and co-digested together with low solid swine wastewater in a novel two-state (liquid/solid) anaerobic digester. The special subject of the two-state digester is that operates with both, liquid and solid fractions, which are present in a segregated form inside the digester. The feeding and the with...

In the present study the potential of bioethanol production using carbohydrate-enriched biomass of the cyanobacterium Arthrospira platensis was studied. For the saccharification of the carbohydrate-enriched biomass, four acids (H2SO4, HNO3, HCl and H3PO4) were investigated. Each acid were used at four concentrations, 2.5 N, 1 N, 0.5 N and 0.25 N, a...

Microalgal biomass seems to be a promising feedstock for biofuel generation. Microalgae have relative high photosynthetic efficiencies, high growth rates, and some species can thrive in brackish water or seawater and wastewater from the food- and agro-industrial sector. Today, the main interest in research is the cultivation of microalgae for lipid...

This paper presents the effects of various phosphorus concentrations (10, 50, 250 and 500 mg l-1 K2HPO4) on the biomass production and composition of Arthrospira (Spirulina) platensis in relation to light intensity (24, 42 and 60 μE m-2 s-1). The maximum biomass production was 3592 ± 392 mg l-1 and this was observed in 250 mg l-1 K2HPO4 at 60 μE m-...

In this study the biomass composition alteration of the cyanobacterium Arthrospira (Spirulina) platensis under various amounts of limited phosphorus is studied. It was observed that the alteration of the compounds of the biomass occurred gradually as the phosphorus became limited. Carbohydrates and lipids increased from about 9% up to 65% and from...

Carbohydrates are a desirable biomass compound for the generation of several biofuels. Phosphorus nutrient limitation causes a significant increase in the carbohydrate content of the cyanobacterium Arthrospira (Spirulina) platensis. Carbohydrates accumulated up to a content of 63.09 ± 3.43% (± SD) in both batch and semi-continuous cultures. In orde...

Recently research interest has focused on the production of biofuel from microalgae. Microalgae are photosynthetic microorganisms that grow utilizing solar energy, nevertheless, the quantities of fertilizers that should be used for their production are enormous. One alternative to the use of synthetic fertilizers is to employ wastes and wastewaters...

In this work, numerous b-values (or buffer index), an output of statistical analysis of titration data of anaerobic digesters content with strong acid and base, have been used to express the anaerobic process status. These data were available in the Lab of Agricultural Structures of A.U.A. from experiments on biogas production during the last decad...

In this paper an older methane production mathematical model for mechanically separated effluents of pig wastes has been enriched with new experimental data of pig and dairy effluents and transformed into the following general one: Methane= (r2 = 0,980). A similar process was also applied to available experimental data of mixtures of such effluents...