Search

The present study aimed to optimize the culture conditions for algal growth and lipid production of Desmodesmus intermedius. Different environmental factors including nitrogen content, salinity, kinetin hormone, vitamin B12, and light intensity were applied individually or in combination using Plackett–Burman statistical experimental design. In addition, the impact of optimized conditions on fatty acids profile and biodiesel quality was studied. Results revealed that the maximum lipid and biomass production for individual study optimization was recorded using 125 mg/L sodium nitrate, 12.5 mg/L sodium chloride, 10−7 mol/L kinetin, and 10−2 mg/L vitamin B12, at 4500 lux. In addition, Plackett-Burman model revealed that combination of sodium nitrate (125 mg/L), sodium chloride (25 mg/L), Kinetin hormone (0 mol/L), vitamin B12 (0 mg/L), and Light intensity (4500 Lux) resulted in maximum lipid productivity. The overall enhancements in lipid productivities using Plaktt–Berman model were 20% and 61.6% over individual optimization and control, respectively. Fatty acids profile for D. intermedius recorded the presence of 14 fatty acids. These fatty acids are suitable to produce high-quality biodiesel. [ABSTRACT FROM AUTHOR]

The present study aimed to isolate and evaluate a local Protosiphon sp. for biodiesel production and antioxidant activity of its residual lipid-free biomass. Phylogenetic analysis confirmed that the isolate is Protosiphon botryoides. In the control medium using 250 mg L−1 NaNO 3 as a nitrogen source, cells showed 37.7 dw% lipid content at stationary phase. At different nitrogen levels, increasing of nitrogen concentration resulted in obvious increase in growth, showing the maximum biomass productivity of 0.133 g L−1 d−1 at middle exponential phase using 750 mg L−1 NaNO 3 , with simultaneous reduction in lipid content, reaching its lowest recorded value of 27.9 dw%. Due to enhancement of lipid content of N-deficient culture (125 mg L−1 NaNO 3), it showed the highest lipid productivity of 41.3 mg L−1 d−1. Fatty acid analysis confirmed the dominance of linoleic acid, eicosatrienoic acid, oleic acid, and palmitic acid. Biodiesel characteristics complied with the international standards and showed better properties than some other reported biodiesel promising microalgae. In addition, lipid-free biomass showed high radical scavenging activity of 55.3%, which confirms its suitability as additional nutritional and pharmaceutical material for enhanced biomass valorization. ∙ A new isolate of Protosiphon was studied as a biodiesel feedstock. ∙ Antioxidant activity of lipid-free biomass was evaluated. ∙ It showed higher lipid content (37.7 dw%) than many biodiesel-promising microalgae. ∙ Highest lipid productivity of 41.3 mg L-1 d -1 was recorded in N-deficient medium. ∙ Lipid-free biomass showed high radical scavenging activity of 55.3%. [ABSTRACT FROM AUTHOR]

Summary: In the present study, eight seaweeds (five red, two brown and one green) were collected and evaluated for dual biodiesel and/or bioethanol production. The highest significant lipid and carbohydrate contents were recorded in the brown seaweed Dilophus fasciola (4.92 and 37.97%dw, respectively). Three routes were investigated, namely R1 and R2 for direct production of biodiesel and bioethanol, respectively, from the whole biomass, in addition to R3 representing the sequential biodiesel and bioethanol production. D. fasciola showed a biodiesel yield of 35.04 mg g−1 dw, composed mainly of C16‐C18 fatty acids with a high saturation degree. All biodiesel characteristics complied with the recommended values of international standards. The maximum reducing sugar content (37.2 g L−1) and bioethanol productivity at 72 hours (0.165 g L−1 h−1) were recorded in the lipid‐free biomass (R3), which were 16.3% and 27.9%, respectively, higher than that of R2. Therefore, a maximum estimated total energy output of 9.96 MJ kg−1 was recorded in R3, which represented 6‐times and 28.3% higher than R1 and R2, respectively. [ABSTRACT FROM AUTHOR]

Summary: In the present study, valorization of food and lignocellulosic wastes into biodiesel and 2‐phenylethanol using Metchinikowia pulcherrima isolated from rotten food wastes was evaluated. At the optimum pH of 5.5, food waste hydrolysate (FWH) showed 74.1% higher dry weight than the corresponding synthetic medium. Rice straw (RS) and softwood sawdust (WWA) were used as additional carbon sources to increase the C:N ratio of FWH. WWA enhanced the biomass production by 23.3% and 55.9% over the corresponding RS and FWH, respectively; while RS enhanced lipid accumulation. Due to enhancement of growth, 75 g WWA showed the maximum recorded lipid productivity of 2.49 g L−1 d−1. Interestingly, both hexoses and pentoses were effectively metabolized. Regarding fatty acid profile of M. pulcherrima, RS‐ and WWA‐enriched growth media showed higher saturated fatty acids proportions (56.9% and 98.3%, respectively, over that of FWH), with better biodiesel characteristics. FWH showed the heights significant production of 2‐phenylethanol up to 56.7 mg L−1 after 96 hours. However, FWH enriched with WWA showed the highest gross energy output of 33.98 GJ m−3 y−1. Thus, the present study suggested an integrated approach of M. pulcherrima cultivation on FWH enriched with WWA for efficient biofuel production through waste recycling. [ABSTRACT FROM AUTHOR]

Nowadays, microalgae are widely discussed as a promising feedstock for biodiesel production due to the legitimate concerns about the consequences of using edible oils. Selection of the most suitable microalgal species relies on several key parameters such as growth rate, lipid productivity and fatty acid profile. In the present study, different species of Scenedesmus were isolated and compared for their efficiency as biodiesel feedstocks. S. obliquus showed the highest biomass productivity of 0.102 g CDW L −1 d −1  at stationary phase. However, S. intermedius showed the highest significant lipid content of 400.9 mg g −1 CDW. Regarding lipid productivity, S. obliquus was the most lipid productive strain at stationary phase with up to 24.94 mg L −1 d −1 , representing 23.9% significant increase over that of S. intermedius . In addition, cetane number and iodine value of S. obliquus FAMEs were 54.12 and 110.37 g I 2 /100 g, respectively. Moreover, FAMEs of S. obliquus showed kinematic viscosity and specific gravity of 1.9–6.0 mm 2  s −1 and 0.88 g cm −3 , respectively, which are in accordance with the international standards. Among the different studied species of Scenedesmus , the present study nominated S. obliquus as a promising renewable feedstock for biodiesel production. [ABSTRACT FROM AUTHOR]

In the present work, a novel approach of using growth medium with different substitutions of lipid-free algal hydrolysate (LFAH, 0, 5, 10 and 15%) and/or waste glycerol (WG, 0, 5, 10 and 20 g L −1 ) for enhanced biodiesel production from Scenedesmus obliquus was studied. Combination of different concentrations of WG with 15% LFAH showed the maximum significant biomass productivity, which represented 27.4, 30.5 and 28.9% over the control at combined 5, 10 and 20 g L −1 WG, respectively. The combinations of different LFAH with 20 g L −1 WG showed the maximum significant lipid accumulation, where lipid productivity showed its maximum significant value of 59.66 mg L −1  d −1 using LFAH15-WG10. In addition, LFAH15-WG10 significantly enhanced total FAMEs yield by 21.2% over the control. Moreover, it reduced polyunsaturated fatty acids (PUFAs) ratio from 52.1% to 47.8% of total FAMEs, and increased monounsaturated fatty acids (MUFAs) ratio from 26.6% to 31.3% of total FAMEs. [ABSTRACT FROM AUTHOR]

Cost-efficient harvesting of microalgae is a major challenge for large-scale biomass production. The present study aimed to optimize and model the flocculation process for efficient harvest of the biodiesel promising green microalga Scenedesmus obliquus grown in municipal wastewater. In addition, the influence of applied flocculation on biodiesel recovery was measured. Ferric sulphate showed the highest relative flocculation efficiency in comparison with the other tested flocculants. At initial OD 680 of 1, the flocculent dose required to achieve 99.5% flocculation efficiency was 150 mg L −1 after 40 min. In addition, relatively higher flocculation efficiencies of S. obliquus cells were observed at lower initial OD 680 . The suggested polynomial model showed satisfactory and accurate results, with high positive correlation (0.956) between the calculated and measured flocculation efficiency. Furthermore, fatty acid methyl esters (FAMEs) yield of the flocculated biomass showed 40.9% significant increase ( P < 0.01) over the centrifuged cells. It can be concluded that flocculation using ferric sulphate is greatly advantageous, as in a single step it served a dual propose of algal biomass harvest and enhanced FAMEs recovery at doses much lower than that used in wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Recently, microalgae have been attracting a wide attention as a source of high-lipid feedstock to produce biodiesel. A total of twenty one halophilic microalgae were isolated from the hypersaline Bardawil lagoon North Sinai, Egypt. Nine of them were further characterized with respect to biomass and fatty acid productivities. Biomass productivity as cellular dry weight (CDW), fatty acid content and, consequently, fatty acid productivity of the chlorophyte Tetraselmis elliptica was the highest among alltested strains (0.122 g CDW L −1 d −1 , 77.36 mg g −1 CDW and 14.1 mg L −1 d −1 , respectively). Lipid fractionation showed that total lipids represented 12.96 mg g −1 CDW and neutral lipids represented 37% of the total lipids with corresponding iodine value of 70.3 g I 2 /100 g oil. In all fractions, C16:0 and C18:1 n -9 were predominant, being as high as 31 and 20% of total fatty acids in neutral lipids, 26 and 24% of total fatty acids in polar lipids and 28 and 26% of total fatty acids in phospholipids, respectively. This study demonstrates that the halophilic microalga T. elliptica isolated from hypersaline water is a promising species for biodiesel feedstock. [ABSTRACT FROM AUTHOR]

Nowadays, fossil fuels; including coal, oil, and natural gas; are the world's primary energy sources required for industry, lighting, transportation and heating. Their needs increased dramatically due to the vast expansion in human population and economy. In contrast, a greenhouse gas emission is a serious problem arose from such uses that might lead to potentially catastrophic changes in the earth's climate. In addition, fossil fuels are limited non-renewable resources that will run out in few decades. These factors motivated many researchers to develop a new renewable energy sources that could replace fossil fuels. Biodiesel is considered as the best candidate for this purpose. Recently, microalgae were discussed as a promising feedstock for biodiesel production. This review presents a critical overview of engineered challenges compilations related to microalgal biomass production. In addition, advantages and current limitations of biodiesel production, quantitative and qualitative feasibility of microalgal biodiesel, and its economic feasibility are discussed. [ABSTRACT FROM AUTHOR]

During the transesterification of oil feedstock for biodiesel production, the reaction primarily happens at the ester bonds where the fatty acid chains meet the glycerol. Therefore, only esterified fatty acids (EFAs) are able to be turned directly into biodiesel by transesterification. In this study, an optimized procedure for EFAs recovery from the biodiesel promising microalga Scenedesmus obliquus was studied. The effect of different solvent mixtures (ratios), extraction times, pretreatments and cell-disruption methods on intracellular EFAs and free fatty acids (FFAs) yield was examined. Using of chloroform:methanol (C:M) 2:1 for 2 h was shown to be the best solvent mixture for lipid extraction which resulted in the highest EFAs yield. Furthermore, testing of different cell-disruption methods showed that cell-disruption is not essential for lipid extraction from S. obliquus cells. Although, microwave pretreatment showed significant increase in EFAs yield with respect to overnight oven drying at 80 °C, all showed insignificant differences to the control. Moreover, overnight cell freezing showed 7.7% significant reduction in EFAs yield with respect to the control, while hot-water treatment for 5 min showed significant increase by 13.7%. On the other hand, overnight cell incubation, in oven or freezing, resulted in significant increase in FFAs up to 7.44 and 12.47 mg g −1 of the dry weight, respectively. In addition, the present study showed that no pretreatment with isopropanol to inactivate the lipases is needed when hot-water pretreatment is performed. This study suggested that hot-water pretreatment not only deactivate lipases, but also enhances the EFAs recovery. [ABSTRACT FROM AUTHOR]

• Agar-free seaweeds were anaerobically digested for biogas production. • Anaerobic digestate was used for microalgal cultivation for biodiesel production. • Agar extraction enhanced biogas yield and biomethane content. • The highest microalgal biodiesel recovery was recorded using 20% digestate. • The suggested approach showed high technical and economic feasibility. The aim of this work was to evaluate a novel integrated biorefinery route for enhanced energy recovery from seaweeds and microalgae. Agar extraction prior to anaerobic digestion recorded the highest biogas productivity of 32.57 L kg−1 VS d−1. Supplementation of the microalgal growth medium with anaerobic digestate from agar-extracted biomass enhanced the microalgal growth, recording the highest dry weight of 4.57 g L−1 at 20% digestate ratio. In addition, lipid content showed the highest value of 25.8 %dw. Due to enhancement of growth and lipid content, 20% digestate ratio showed the highest lipid productivity and FAMEs recovery (65.2 mg L−1 d−1 and 123.3 mg g−1dw, respectively), with enhanced biodiesel characteristics. The present study estimated annual revenue of 1252.7 US$ ton−1 from the whole Gracilaria multipartita biomass conversion into biogas, while that through agar extraction deserved 36087.0 US$ ton−1, with enhanced annual biodiesel yield by 69.7% over the control medium. [ABSTRACT FROM AUTHOR]

• Different current methods of FOG management were compared. • The challenges in biodiesel production from FOG were discussed. • Pros and cons of FOG pretreatment for biodiesel production were outlined. • FOG-biodiesel possesses future potential to replace petroleum diesel. • Integrated approaches for biofuel production from FOG are of great importance. • More research focus is needed for enhancement of brown grease conversion. Wastewater discharges from restaurants, kitchens, food processing plants and slaughterhouses contain high proportion of fat, oil, and grease (FOG). Critical overview on the attractive features, current state, and needed advancements are timely essential for FOG-derived biodiesel production. Although FOG conversion into biodiesel does not compete with human food, the high contents of moisture and free fatty acids (FFAs) are the main challenges for FOG efficient utilization. The present review discussed the various methods of high FFAs-lipidic feedstocks pretreatment including acid esterification, steam stripping, nanocatalytic technology, biological conversion, glycerolysis, supercritical esterification, and simultaneous in situ conversion. Comparing to other feedstocks, FOG-derived biodiesel showed better characteristics concerning oxidative stability, flash point, cetane number, and total emissions. In addition, most of the FOG-derived biodiesel fuel met the recommendations of the international standards as well as conventional diesel. Due to its lower price, the economic analysis showed that FOG is a strong competitor to other biodiesel feedstocks. The decrease in feedstocks availability, continuous rise in the crude oil prices, life threatening environmental deterioration, and food-versus-fuel debate support FOG to be a potential biodiesel feedstock in the near future. However, the cost of FOG-biodiesel production is still far away from the acceptable ranges to compete fossil diesel. Lastly, this paper suggested a number of future perspectives in order to enhance the economy and feasibility of FOG-derived biodiesel including developing new methods for efficient conversion of brown grease, integrated approaches for sequential production of biofuels from FOG, and co-esterification of FOG with other lipidic feedstocks. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• A new halophilic Dunaliella salina KSA-HS022 was isolated from hypersaline lagoon. • Stepwise adaptation showed the highest biomass productivity of 0.191 g−1 L−1 d−1 at 125‰. • Oxidative stress markers of the control were significantly higher than the adapted. • Adapted culture showed the highest FAMEs productivity of 50.3 mg L−1 d−1 at 150‰. • Stepwise adaptation enhanced the biodiesel yield and characteristics. In the present study, a halophilic microalgal species was isolated from a hypersaline lagoon with salinity average of 45.3‰ and identified as Dunaliella salina KSA-HS022. It was further cultivated at a salinity range of 50–250‰, applied directly to batch cultures or through stepwise increase in a semi-continuous culture. The later showed the highest biomass productivity of 0.191 g L−1 d−1 at 125‰, which represented 45.8% higher than the corresponding batch culture (control). Oxidative markers in the control cultures were significantly higher than those of the adapted culture, confirming reduction of oxidative stress by adaptation. In addition, stepwise adaptation showed the highest lipid productivity of 56.5 mg L−1 d−1 at 150‰ (39.9% higher than the corresponding control), which resulted in the highest fatty acid methyl esters productivity. Moreover, stepwise increase of salinity up to 150‰ enhanced the biodiesel characteristics, offering a new route for enhanced biodiesel production at extraordinary salinity levels. [ABSTRACT FROM AUTHOR]

• Different LEDs were used for night illumination of Scenedesmus obliquus. • Used LEDs were white, blue, green and red. • Red and blue LEDs individually enhanced lipid production. • Growth and lipid production further enhanced by combined blue-red LEDs. • Combined blue-red LEDs enhanced biodiesel yield and characteristics. The present study investigated the effect of monochromatic light-emitting diodes (LEDs) on the growth and biodiesel yield of the green microalga Scenedesmus obliquus. Different LEDs were applied individually or in combination during the night period. Among different individual treatments, red and blue illumination showed the highest biomass and lipid productivity due to stimulation of pigmentation and photosystem II, respectively. Microalgal growth, lipid production and biodiesel recovery significantly increased under combined blue-red illumination. In addition, saturated and monounsaturated fatty acids proportions increased in favor of polyunsaturated ones. Moreover, blue-red LEDs enhanced the net biodiesel energy output over the control. The total increase in net energy output represented 5.1, 3.8 and 10.8 MJ using red, blue and blue-red light, respectively. In conclusion, application of blue-red LEDs during the night period is an economical technology for microalgae cultivation, which might have a potential impact on the future of commercial biodiesel production from microalgae. [ABSTRACT FROM AUTHOR]

In the present study, biomass and lipid production of the biodiesel promising green microalga Tetradesmus obliquus BPL16 were studied by application of p -coumaric acid as a suggested novel growth regulator found predominantly in phenolics-rich streams. It was used in its pure form along with two phytohormones (jasmonic acid and salicylic acid). Using 100 μM jasmonic acid, 10 μM salicylic acid and 1 mM p- coumaric acid improved biomass production by 85.4%, 54.9% and 34.1%, respectively, over the control. In addition, significant increments in lipid content by 22%, 105.6%, and 145.4%, respectively, over the control were obtained at the aformentioned concentrations. Neutral lipids were significantly improved under elicitor-supplemented conditions. Moreover, fatty acid methyl esters (FAMEs) profile was also vitally influenced with drastic increase in oleic acid (C18:1) proportion by 81.7% and 73.6% over the control at 10 μM of jasmonic acid and 1 mM of p- coumaric acid, respectively. Application of p- coumaric acid resulted in estimated biodiesel energy output of 10.8 MJ kg−1 which represented 141% and 9.4% higher than the control and jasmonic acid, respectively. In conclusion, the present study suggested p- coumaric acid as a novel growth regulator for instant synchronized growth and lipid accumulation in microalgae for enhanced biodiesel production. Image 1 • Two phytohormones along with p -coumaric acid were compared. • p -Coumaric acid is a phenolic compound found predominantly in waste streams. • p -Coumaric acid enhanced the lipid production by 240% over the control. • Optimized conditions enhanced the FAME profile. • Total energy output due to p -coumaric acid represented 141% higher than the control. [ABSTRACT FROM AUTHOR]

Abstract Screening of native microalgal species for different biotechnological applications is a key step to achieve a strong algal database with successful commercial applications. In the present study, a new strain namely Nannochloropsis oceanica NIOF15/001 was isolated and identified phylogenetically using rbc L and the newly designed Cyt -c as an alternative molecular marker. The late exponential phase of the isolate was recorded at the 10th day of growth in f/2 medium, with a maximum cellular dry weight (CDW) of 0.722 g L−1 and relatively high lipid content of 37.7% of CDW. The isolate showed biomass and lipid productivities of 75.6 and 28.6 mg L−1 day−1, respectively. The recorded biomass productivity in the current study was 1.4, 3.0, 3.6 and 2.0 times higher than that recorded in the previous studies for N. oceanica IMET, N. oce anica CASACC201, N. oceanica DUT01 and N. oceanica CCNM 1081, respectively. In general, values of cetane number (52.3), iodine value (94.7 g I 2 /100 g oil), cold filter plugging point (4.7 °C) and kinematic viscosity (3.97 mm2 s−1) of the produced fatty acid methyl esters complied with those recommended by international standards. Furthermore, application of 0.1 g L−1 of lipid-free dry biomass enhanced Artemia survival by 500% and growth by 40%. The present study suggested the new isolate N. oceanica NIOF15/001 as a promising marine microalga for dual use in aquaculture and biodiesel production. Graphical abstract Image 1 Highlights • Nannochloropsis oceanica NIOF15/001 was identified using Cyt-c and rbc L markers. • The maximum cellular dry weight was 0.722 g L-1 with lipid content of 37.7%. • Biomass and lipid productivities were 75.6 and 28.6 mg L-1 day-1, respectively. • Estimated FAMEs characteristics complied with the international standards. • 0.1 gL-1 of lipid-free biomass enhanced Artemia survival by 500% and growth by 40%. [ABSTRACT FROM AUTHOR]

Commercialization of microalgal biofuels is not yet attained even after plentiful of research and extensive scientific projects. Expending the cost and energy for producing single microalgal product proven to be unviable, and hence integrating multiple product generation from single batch of biomass was considered as effective. This review focusses on delineating the challenges associated with individual fuel production pathways and merits of integrating different fuel production pathways. The advantages of integrated microalgal biorefinery have been summarized along with energy output and economic impact. Integrated production of different biofuels enhances the energy output significantly (biodiesel + biocrude oil - 18.8 MJ kg−1, biodiesel + bioethanol - 15.4 MJ kg−1, biodiesel + biogas - 13.4 MJ kg−1) and reduced the cost of biomass production by about 60% and 40% for biodiesel and other fuel productions, respectively. In addition, the integrated production of bioproducts with fuels also emphasized in the present study. [Display omitted] • Technological progress in microalgal fuels is yet to attain commercial feasibility. • Integration of different biofuel productions is inevitable for cost effectiveness. • Increased energy outputs (MJ kg−1) 15.4 and 18.8 were attained on integration. • Integration resulted in cost reduction by 60% in biomass production for biodiesel. • Integrated production of fuel and bioproduct seems attractive and lucrative. [ABSTRACT FROM AUTHOR]

In the present study, a new biorefinery approach for efficient conversion of chicken manure mixed with rapeseed straw was investigated through anaerobic co-digestion though digestate recycling. The liquid digestate fraction was used for straw pretreatment, while solid fraction was utilized for rearing the black soldier fly larvae. Anaerobic digestion of raw straw resulted in biomethane yield of 144.2 L kg−1 VS, while the pretreatment enhanced it to 227.6 L kg−1 VS. Co-digestion of the pretreated straw with chicken manure at different ratios of 1:1, 1:3, and 3:1 increased the biomethane yield to 323.5, 349.6, and 262.3 L kg−1 VS, respectively, with higher biomethanation efficiency. Black soldier fly larvae were grown on different ratios of solid digestate/larva (D/L) of 0.25, 0.50, 0.75 and 1.00, where it showed higher growth and faster development by increasing the digestate ratio. In addition, lipid content significantly increased by increasing the digestate ratio, reaching the maximum values of 31.8 dw% at 1.00 D/L. Therefore, the highest fatty acid methyl esters recovery of 301.8 mg g−1 dw was recorded at 1.00 D/L, with pronounced enhanced biodiesel characteristics. The suggested integrated approach using a mixture of liquid digestate-pretreated straw to manure at a ratio of 1:3 for dual purpose of biogas and biodiesel production enhanced the gross bioenergy yield by 95.7%, 24.6%, and 38.7% over those of raw rapeseed straw, pretreated straw, or chicken manure, respectively. The present study demonstrates an innovative waste-to-energy route that will have a positive impact on the future of biofuel industry. Image 1 • Rapeseed straw was co-digested with chicken manure. • Digestate was used for rapeseed straw pretreatment and larvae rearing. • Highest biomethane yield was recorded using 1:3 co-digestion ratio. • Biomethanation efficiency showed the maximum value using 1:3 ratio. • Digestate/larva ratio of 1.0 showed the maximum biodiesel yield. [ABSTRACT FROM AUTHOR]

The freshwater microalga Chlorella vulgaris MSU AGM 14 was cultured at different CO 2 conditions (up to 8%) with 100 μmol photons m−2 s−1 to evaluate biomass and lipid productivity. For effective extraction of intra-cellular lipids, a novel method based on mild pressure (1–2.5 kg/cm2) with short period (5–15 min) of heat shock (50–70 °C) were studied for the wet biomass. The transesterified lipids were qualitatively and quantitatively analysed using Gas Chromatography coupled with Mass Spectrometry (GC-MS). The higher CO 2 aeration (8%) significantly increased the biomass productivity (23%) when compared with control and CO 2 (4%) aeration. Total lipid production (93%) acquired by conventional extraction procedure showed enhanced production simultaneously. The maximum lipid recovery (0.225 g g−1 dw) was obtained at a pressure of 2 kg/cm2 and heating for 10 min at 60 °C. The transesterified lipids showed that oleic acid (C18:1–51.62%) was the main component in both conventional and suggested lipid extraction process. The suggested extraction process showed significant increase in biodiesel yield by 26.7%. The energy outputs of biodiesel by conventional and suggested extraction process were 417.7 and 533.6 MJ ton−1, respectively. The overall results indicated that 8% of CO 2 induced the biomass and lipid productivity by 94% and 54.8%, respectively, when compared with control. In addition, the suggested mild pressure with heat shock extraction process further enhanced the lipid recovery by 21% which serves as a cost-effective lipid extraction process for microalgae. Image 1 • Elevated CO 2 (8%) promoted biomass (23%) and lipid productivity (94%). • Mild pressure with heat shock evidenced 12.5% additional recovery of total lipids. • Suggested extraction increased 1.96% of PUFA and 0.58% of MUFA recovery. • FAMEs of suggested process proved 27.8% elevated energy output. [ABSTRACT FROM AUTHOR]

• Chlorella vulgaris inoculum was pretreated with plasma jet for different times. • Plasma jet contained reactive species, mainly N 2 and OH radicals. • Pretreatment for 30 and 60 s increased the lipid content by 7.5% and 6.9%, respectively. • Pretreatment for 60 s showed the highest biodiesel production (998.1 mg L−1). • Pretreatment for 60 s showed the maximum gross energy output of 10.70 kJ L-1. In the present study, a high-throughput procedure was employed to enhance biodiesel recovery from the green microalga Chlorella vulgaris through pretreatment of inoculum with low doses of cold atmospheric-pressure plasma (CAPP). Pretreatment for 30 s resulted in significant increase in the colony-forming unit (CFU) by 26.6% over the control, and recorded the highest biomass productivity of 0.193 g L−1 d−1. In addition, the average cellular chlorophyll content was 18.7% and 23.3% higher than the control and 60 s, respectively. Moreover, short exposure times (30 and 60 s) significantly increased lipid content by 7.5% and 6.9%, respectively, over the control. Because 30 s pretreatment enhanced both growth and lipid content, the volumetric lipid productivity (40.7 mg L−1 d−1) increased by 16.6% and 17.6% over the control and 60 s, respectively. Interestingly, pretreatment for 60 s showed the maximum fatty acid methyl esters (FAMEs) recovery of 478.7 mg g−1 dw, which confirms lipid accumulation in the form of glycerides due to plasma stress. Therefore, the maximum volumetric FAMEs production (998.1 mg L−1) was recorded in the culture inoculated with 60 s-exposed cells, which was 43.5% and 15.7% higher than that of the control and 30 s, respectively. Overall, pretreatment for 60 s resulted in the maximum gross energy output (GEO Add) of 10.70 kJ L−1, which was 79.5% higher than that of 30 s. In conclusion, the current study represents a novel approach for sustainable production of biodiesel from microalgae through inoculum exposure to a low-dose of CAPP. [ABSTRACT FROM AUTHOR]

Generation of biodiesel from microalgae grown in wastewater can offer a cost-effective approach, whilst wastewaters usually do not contain the optimum concentrations of the essential nutrients and carbon sources that result in lowering the productivities of biomass and lipid. This study aimed to overcome this limitation by manipulating wastewater with various concentrations of nutrients (NO 3 −, PO 4 3−, Cl− and SO 4 2−) and three carbon sources either individually or in combination to cultivate Micractinium reisseri for biodiesel production. Initially, various dilutions of wastewater were tested and a concentration up to 75% of wastewater showed the highest biomass productivity (0.076 g L−1 d−1) and lipid productivity (0.014 g L−1 d−1). The optimum manipulating conditions for maximum lipid production and the highest productivity required 50% decrease in phosphorous from the concentration of the control medium and supplementation with 1.0 g L−1 of glucose. Under this condition, biomass and lipid productivities increased by 1.7 and 4-folds, respectively, compared to those observed in the control. Furthermore, phosphorous starvation condition in the presence of glucose significantly improved fatty acid profile in the biomass and biodiesel quality related parameters. Image 10895849 • M. reisseri was grown in wastewater under various stress conditions for biodiesel production. • Diluted wastewater up to 75% showed maximum biomass productivity (0.076 g L−1 d−1). • Combined stress conditions were favourable for improving lipid productivity. • Phosphorus depletion and glucose supplementation improved lipid productivity by 4-folds. • Phosphorus starvation and glucose supplementation enhanced biodiesel quality. [ABSTRACT FROM AUTHOR]