Search

Models for anaerobic digestion of lipid-rich waste taking inhibition into account were reviewed and, if necessary, adjusted to the ADM1 model framework in order to compare them. Experimental data from anaerobic digestion of slaughterhouse waste at an organic loading rate (OLR) ranging from 0.3 to 1.9 kgVS m −3 d −1 were used to compare and evaluate models. Experimental data obtained at low OLRs were accurately modeled whatever the model thereby validating the stoichiometric parameters used and influent fractionation. However, at higher OLRs, although inhibition parameters were optimized to reduce differences between experimental and simulated data, no model was able to accurately simulate accumulation of substrates and intermediates, mainly due to the wrong simulation of pH. A simulation using pH based on experimental data showed that acetogenesis and methanogenesis were the most sensitive steps to LCFA inhibition and enabled identification of the inhibition parameters of both steps. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effectiveness of cultivating Parachlorella kessleri and Acutodesmus obliquus , in anaerobic digestion effluent (ADE) derived from the co-digestion of end-of-life dairy products with mixtures of agro-industrial wastes. To this end, their performance under sterile and non-sterile conditions and different ADE loadings was evaluated, in terms of biomass and lipid production, nutrient removal efficiency and vitality of the photosynthetic apparatus. 10% (v/v) ADE loading inhibited growth over 9–12 days of cultivation, however biomass yields of 1.1 and 1 g L −1 , 22.7% and 19.5% (w/w) fatty acids concentration, as well as NH 3 -N assimilation of 49.7 mg L −1 and 32.3 mg L −1 and TP removal of 84.2% and 84% were recorded for P. kessleri and A. obliquus , respectively. Among all the ADE-based treatments tested, P. kessleri outperformed A. obliquus , with no differences observed between sterilized and non-sterilized ADE. [ABSTRACT FROM AUTHOR]

Cultivation of microalgae Chlorella sp. with livestock waste compost as an alternative nutrient source was investigated in this present study. Five culture media with different nutrient concentrations were prepared. The characteristics of algal growth and lipid production were examined. The results showed that the specific growth rate together with biomass and lipid productivities was different among all the cultures. As the initial nutrient concentration decreased, the lipid content of Chlorella sp. increased. The variations in lipid productivity of Chlorella sp. among all the cultures were mainly due to the deviations in biomass productivity. The livestock waste compost medium with 2000 mg L −1 COD provided an optimal nutrient concentration for Chlorella sp. cultivation, where the highest productivities of biomass (288.84 mg L −1 day −1 ) and lipid (104.89 mg L −1 day −1 ) were presented. [ABSTRACT FROM AUTHOR]

The present study investigates the effect of spent media of acetogenic dark fermentation for mixotrophic algal cultivation for biodiesel production. Mixotrophic growth conditions were optimized in culture flask (250 mL) using Chlorella sp. MJ 11/11. Maximum lipid accumulation (58% w/w) was observed under light intensity, pH, nitrate and phosphate concentration of 100 μmol m −2 s −1 , 7, 2.7 mM and 1.8 mM, respectively. Air lift (1.4 L) and flat panel (1.4 L) reactors were considered for algal cultivation. Air lift showed significant improvement in biomass and lipid production as compared to flat panel reactor. The results could help in development of sustainable technology involving acetogenic hydrogen production integrated with sequential mitigation of spent media by algal cultivation for improved energy recovery. [ABSTRACT FROM AUTHOR]

The aim of this work is to compare the life cycle assessments of low-N and normal culture conditions for a balance between the lipid content and specific productivity. In order to achieve the potential contribution of lipid content to the life cycle assessment, this study established relationships between lipid content (nitrogen effect) and specific productivity based on three microalgae strains including Chlorella , Isochrysis and Nannochloropsis . For microalgae-based aviation fuel, the effects of the lipid content on fossil fuel consumption and greenhouse gas (GHG) emissions are similar. The fossil fuel consumption (0.32–0.68 MJ·MJ −1 MBAF) and GHG emissions (17.23–51.04 g CO 2 e·MJ −1 MBAF) increase (59.70–192.22%) with the increased lipid content. The total energy input decreases (2.13–3.08 MJ·MJ −1 MBAF, 14.91–27.95%) with the increased lipid content. The LCA indicators increased (0–47.10%) with the decreased nitrogen recovery efficiency (75–50%). [ABSTRACT FROM AUTHOR]

The present study aimed to develop thermo-tolerant mutants of Chlorella pyrenoidosa NCIM 2738 for high lipids production. For this, ethyl methane sulfonate was used, which generated two effective thermo-tolerant mutants, M18 and M24 of Chlorella pyrenoidosa NCIM 2738, capable of surviving at temperature up to 47 °C and showing improved lipid and biomass yields. They showed 59.62% and 50.75% increase, respectively in lipid content compared to wild type at 30 °C, which could not grow at temperature above 35 °C. The novelty of this study lied in incorporation of PAM Flurometry with mutagenesis to generate thermo-tolerant mutants of C. pyrenoidosa and investigating the reasons for increased yields of mutants at cellular and photosynthetic levels with the aim to use them for commercial biodiesel production. [ABSTRACT FROM AUTHOR]

The objective of this work was to study the kinetics of lipid production at lab scale fermenters by a new isolate of Yarrowia lipolytica SKY7. The model terms glycerol concentration inoculum and C/N ratio with inoculum were found to be significant for lipid production. Lipid production was found to be higher in glycerol 82.5 g/L, C/N ratio 75 and inoculum volume 6.25%. Optimized culture conditions were tested at 15 L bench scale reactor. The biomass concentration and lipid content obtained was 29.5 g/L and 50% (w/w), respectively. The yield coefficients were calculated and found to be 0.332 g/g (g biomass/g of glycerol) of biomass and 0.179 g/g (g lipid/g glycerol consumed) for lipid. Observed rates of lipid production show lipid production from 30 h of fermentation. Out of the total glycerol consumed, 41.1% glycerol was converted into biomass, lipid, and citric acid. [ABSTRACT FROM AUTHOR]

The present study was conducted with microalga Nannochloropsis sp. to evaluate its tolerance responses and biofuel perspectives under different arsenic regime (0–1000 μM As(III)). Results showed that optimal biomass (61.00 ± 3.72 mg/L/d) and lipid productivity (20.27 mg/L/d) were obtained in culture treated with 100 μM As(III) in comparison to other treatments. In addition, fatty acid profile of alga was in accordance with European biodiesel standards (EN 14214), which reflects good oxidative stability of oil. High antioxidants viz., ascorbic acid, GSH and cysteine tolerance responses as well as lipid yield at 100 μM As(III), opens a new insight in the field of algal biology. Thus, microalgae Nannochloropsis sp. may be employ in remediation as well as biodiesel production. [ABSTRACT FROM AUTHOR]

In order to produce biodiesel from lipids in wet microalgae with graphene oxide (GO) as solid acid catalyst, the effects on lipids conversion efficiencies of catalyst dosage, transesterification temperature, reaction time, methanol dosage and chloroform dosage were investigated. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and elemental analysis revealed that GO contained 0.997 mmol SO 3 H groups per gram and high amounts of OH groups. Scanning electron microscopy showed that wet microalgae cells were adsorbed on hydrophilic GO surfaces covered with many OH groups. Lipids extracted by chloroform from microalgal cells were transformed into fatty acids methyl esters (FAMEs) through transesterification catalyzed by the acid centers (SO 3 H groups) in GO catalysts. The lipids conversion efficiency into FAMEs was 95.1% in microwave-assisted transesterification reactions of 5 wt.% GO catalyst at 90 °C for 40 min. [ABSTRACT FROM AUTHOR]

This study investigates the year-round production potential and quality of biodiesel from wastewater treatment high rate algal pond (WWT HRAP) biomass and how it is affected by CO 2 addition to the culture. The mean monthly pond biomass and lipid productivities varied between 2.0 ± 0.3 and 11.1 ± 2.5 g VSS/m 2 /d, and between 0.5 ± 0.1 and 2.6 ± 1.1 g/m 2 /d, respectively. The biomass fatty acid methyl esters were highly complex which led to produce low-quality biodiesel so that it cannot be used directly as a transportation fuel. Overall, 0.9 ± 0.1 g/m 2 /d (3.2 ± 0.5 ton/ha/year) low-quality biodiesel could be produced from WWT HRAP biomass which could be further increased to 1.1 ± 0.1 g/m 2 /d (4.0 ton/ha/year) by lowering culture pH to 6–7 during warm summer months. CO 2 addition, had little effect on both the biomass lipid content and profile and consequently did not change the quality of biodiesel. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the feasibility of using lipid-accumulating microalgae to remove cephalosporin antibiotics 7-amino cephalosporanic acid (7-ACA) from wastewater with the additional benefit of biofuels production. Three isolated microalgal strains (namely, Chlorella sp. Cha-01, Chlamydomonas sp. Tai-03 and Mychonastes sp. YL-02) were cultivated under 7-ACA stress and their biomass productivity, lipid production and N-NO 3 − consumption were monitored. It was found that 7-ACA had slight inhibition effects on the microalgal growth at the ratio of 12.0% (Cha-01), 9.6% (YL-02), 11.7% (Tai-03). However, lipid accumulation in the three microalgae was not influenced by the presence of 7-ACA. The investigation on the 7-ACA removal mechanisms during microalgal growth shows that 7-ACA was mainly removed by microalgae adsorption as well as hydrolysis and photolysis reactions. This study demonstrates that using microalgae to treat antibiotic-containing wastewater is promising due to the potential of simultaneous antibiotic removal and biofuel production. [ABSTRACT FROM AUTHOR]

The goal of the present study was to investigate the pH range that can support the growth of C. vulgaris , and, more specifically, to identify the optimal pH for the microalga’s growth, under heterotrophic conditions. Furthermore, the effect of pH on the accumulation of intracellular lipids was studied. A wide range of pH values was tested using the respective buffer solutions. The optimal pH for biomass growth and lipid accumulation under sulfur limitation was found to be 7.5, resulting in maximum specific growth rate of 0.541 days −1 and maximum total lipid content of 53.43% g g DW −1 . The fatty acid composition of C. vulgaris was found to be unrelated to pH, as the lipid content did not present significant variations in the pH values tested. The fatty acid profile was mainly composed of monounsaturated fatty acids (MUFAs) with the dominant one being oleic acid (C18:1). [ABSTRACT FROM AUTHOR]

In the present work we wanted to know what happens during time to biomass and lipid productivities of Chlorococcum littorale repeatedly subjected to N-starvation. Experiments were done using repeated cycles of batch-wise N run-out (after 2 days N = 0). Two different cycles were used: repeated short-starvation (6 days of N = 0) over a total period of 72 days and repeated long-starvation (13 days of N = 0) over a total period of 75 days. Batches (using fresh inocula) were done separately as control. Shorter and longer periods of starvation showed no differences in biomass productivities and PSII quantum yield evolution. The repeated short-starvation-batches showed the same lipid productivities as the control short-starvation batches. Most importantly, the biomass lipid content was the same between control and repeated-batches. Altogether, the results point to C. littorale as a resilient and stable strain, with potential to be used under semi continuous cultivation. [ABSTRACT FROM AUTHOR]

Oleaginous microalgae Nannochloropsis sp. was selected as potential strain for CO 2 mitigation into lipids and pigments. The synergistic effects of light intensity and photoperiod were evaluated to provide the adequate light energy for this strain. The saturation light intensity was 60 μmol·photon·m −2 s −1 . With full illumination, the biomass obtained was 0.850 ± 0.16 g·L −1 with a lipid content of 44.7 ± 1.2%. The pigments content increased with increasing light energy supply. Three main operating factors including initial cell concentration, CO 2 content and gas flow rate were optimized through Response Surface Methodology. The feedings with low CO 2 content at high gas flow rate gave the maximum biomass but with low lipid content. After optimization, the biomass and lipid production were increased up to 1.30 ± 0.103 g·L −1 and 0.515 ± 0.010 g·L −1 , respectively. The CO 2 fixation rate was as high as 0.729 ± 0.04 g·L −1 d −1 . The fatty acids of Nannochloropsis sp. lipids were mainly C16-C18 indicating its potential use as biodiesel feedstocks. [ABSTRACT FROM AUTHOR]

The effects of light-emitting diode (LED) wavelength, light intensity, nitrate concentration, and time of exposure to different LED wavelength stresses in a two-phase culture on lipid production were evaluated in the microalga, Picochlorum atomus . The biomass produced by red LED light was higher than that produced by purple, blue, green, or yellow LED and fluorescent lights from first phase of two-phase culture. The highest lipid production of P. atomus was 50.3% (w/w) with green LED light at 2 days of second phase as light stress. Fatty acid analysis of the microalgae showed that palmitic acid (C16:0) and linolenic acid (C18:3) accounted for 84–88% (w/w) of total fatty acids from P. atomus . The two-phase culture of P. atomus is suitable for biofuel production due to higher lipid productivity and favorable fatty acid composition. [ABSTRACT FROM AUTHOR]

Filamentous microalgae Tribonema is promising for biodiesel production in terms of high lipid content, easy harvesting and good contamination tolerance. As high lipid productivity is a key basis, several methods including different culture medium, phosphorus, iron and CO 2 inductions were tested to enhance lipid productivity in Tribonema minus . T. minus subjected to BG11-freshwater medium achieved a favorable lipid productivity of 216.18 mg L −1 d −1 , much higher than those in other culture medium (BG11-S, Kuhl, f/2, f, 2f, BBM, ASW and ES). Secondly, the optimal phosphorus, iron and CO 2 concentrations for high lipid productivity of T. minus were obtained, respectively. Finally, the cells of T. minus grown in optimized BG11 medium containing 80 mg L −1 KH 2 PO 4 and 6 mg L −1 FeC 6 H 5 O 7 ·NH 4 OH with 2% CO 2 achieved a lipid productivity of 384.67 mg L −1 d −1 , representing a 1.56-fold increase from the control. Therefore, the strategy to enhance lipid productivity of T. minus was successfully proposed. [ABSTRACT FROM AUTHOR]

This study evaluates the effect of different concentrations of glucose supplementation on growth, lipid accumulation, and the fatty acid profile in the Auxenochlorella protothecoides . Addition of glucose promoted the growth rate and decreased the chlorophyll content. Compared with photoautotrophic cells, an increase in the lipid content was observed in mixotrophic cells. The glucose addition induced changes in the fatty acid profile. Higher content of saturated fatty acids was found in the case of cells growing in the glucose-free medium. Oleic acid was the predominant component in mixotrophic cells supplemented with 5 g L −1 glucose, while linoleic acids dominated in cultures supplemented with both 1 and 3 g L −1 glucose. The use of glucose was associated with decreased levels of linolenic acid and PUFA. The changes in the fatty acid profile in mixotrophic cells are favourable for biodiesel production. [ABSTRACT FROM AUTHOR]

Oleaginous yeast Trichosporon cutaneum is robust to high levels of lignocellulose derived inhibitor compounds with considerable lipid accumulation capacity. The potential of lipid accumulation of T. cutaneum ACCC 20271 was investigated using corn stover hydrolysates with varying sugar and inhibitor concentrations. Biodiesel was synthesized using the extracted lipid and the product satisfied the ASTM standards. Among the typical inhibitors, T. cutaneum ACCC 20271 is relatively sensitive to furfural and 4-hydroxybenzaldehyde, but strongly tolerant to high titers of formic acid, acetic acid, levulinic acid, HMF, vanillin, and syringaldehyde. It is capable of complete degradation of formic acid, acetic acid, vanillin and 4-hydroxybenzaldehyde. Finally, the inhibitor degradation pathways of T. cutaneum ACCC 20271 were constructed based on the newly sequenced whole genome information and the experimental results. The study provided the first insight to the inhibitor degradation of T. cutaneum and demonstrated the potentials of lipid production from lignocellulose. [ABSTRACT FROM AUTHOR]

A comprehensive mathematical model involving NPK-10:26:26 fertilizer, NaCl, NaHCO 3 , light and temperature operating variables for Dunaliella tertiolecta cultivation is formulated to predict microalgae-biomass and lipid productivity. Proposed model includes Monod/Andrews kinetics for the absorption of essential nutrients into algae-biomass and Droop model involving internal nutrient cell quota for microalgae growth, assuming algae-biomass is composed of sugar, functional-pool and neutral-lipid. Biokinetic model parameters are determined by minimizing the residual-sum-of-square-errors between experimental and computed microalgae-biomass and lipid productivity using genetic algorithm. Developed model is validated with the experiments of Dunaliella tertiolecta cultivation using air-agitated sintered-disk chromatographic glass-bubble column and the effects of operating variables on microalgae-biomass and lipid productivity is investigated. Finally, parametric sensitivity analysis is carried out to know the sensitivity of model parameters on the obtained results in the input parameter space. Proposed model may be helpful in scale-up studies and implementation of model-based control strategy in large-scale algal cultivation. [ABSTRACT FROM AUTHOR]

The lipid extraction from the microbial biomass is a tedious and high cost dependent process. In the present study, detergent assisted lipids extraction from the culture of the yeast Yarrowia lipolytica SKY-7 was carried out. Response surface methodology (RSM) was used to investigate the effect of three principle parameters (N-LS concentration, time and temperature) on microbial lipid extraction efficiency % (w/w). The results obtained by statistical analysis showed that the quadratic model fits in all cases. Maximum lipid recovery of 95.3 ± 0.3% w/w was obtained at the optimum level of process variables [N-LS concentration 24.42 mg (equal to 48 mg N-LS/g dry biomass), treatment time 8.8 min and reaction temperature 30.2 °C]. Whereas the conventional chloroform and methanol extraction to achieve total lipid recovery required 12 h at 60 °C. The study confirmed that oleaginous yeast biomass treatment with N-lauroyl sarcosine would be a promising approach for industrial scale microbial lipid recovery. [ABSTRACT FROM AUTHOR]

In this paper, the components of amino acids in mixed starch wastewater (corn steep water/corn gluten water = 1/3, v/v) were analyzed by GC–MS. Effects of amino acids on lipid production by Rhodotorula glutinis and COD removal were studied. The results showed that mixed starch wastewater contained 9 kinds of amino acids and these amino acids significantly improved the biomass (13.63 g/L), lipid yield (2.48 g/L) and COD removal compared to the basic medium (6.23 g/L and 1.56 g/L). In a 5 L fermentor containing mixed starch wastewater as substrate to culture R. glutinis , the maximum biomass, lipid content and lipid yield reached 26.38 g/L, 28.90% and 7.62 g/L, with the associated removal rates of COD, TN and TP reaching 77.41%, 69.12% and 73.85%, respectively. The results revealed a promising approach for lipid production with using amino acids present in starch wastewater as an alternative nitrogen source. [ABSTRACT FROM AUTHOR]

Solvent-free microalgal lipid recovery is highly desirable for safer, more sustainable and more economical microalgal oil production. Dispersed air flotation and centrifugation were evaluated for the ability to separate oil and debris from a slurry mixture of osmotically fractured Chaetoceros muelleri cells with and without utilizing collectors. Microalgal oil partially phase-separated as a top layer and partially formed an oil-in-water emulsion. Although collectors, such as sodium dodecyl sulphate enhanced selective flotation, by just adjusting the pH and cell concentration of the mixture, up to 78% of the lipids were recovered in the froth. Using centrifugation of fractured microalgal slurry resulted in removal of 60% cell debris and up to 68.5% of microalgal oil was present in the supernatant. Both methods, centrifugation and flotation provided options for separation of microalgal oil from C . muelleri slurry with similar fatty acid recoveries of 57% and 60%, respectively. [ABSTRACT FROM AUTHOR]

A one-stage cultivation process of the microalgae Scenedesmus obtusiusculus with medium based on natural water sources was developed to enhance lipids and carbohydrates. A medium based on artificial sea water, Baltic Sea water and river water with optimized nutrient concentrations compared to the standard BG-11 for nitrate (−75%), phosphate and iron (−90%) was used for cultivation. Although nitrate exhaustion over cultivation resulted in nitrate limitation, growth of the microalgae was not reduced. The lipid content increased from 6.0% to 19.9%, an increase in oleic and stearic acid was observed. The unsaponifiable matter of the lipid fraction was reduced from 19.5% to 11.4%. The carbohydrate yield rose from 45% to 50% and the protein content decreased from 32.4% to 15.9%. Using natural water sources with optimized nutrient concentrations could open the opportunity to modulate biomass composition and to reduce the cultivation costs. [ABSTRACT FROM AUTHOR]

The biomass of Chlorella sp. was pretreated with three different aqueous deep eutectic solvents (aDESs), i.e. aqueous choline chloride-oxalic acid (aCh-O), aqueous choline chloride-ethylene glycol (aCh-EG) and aqueous urea-acetamide (aU-A). The effect of aDESs pretreatment of microalgae biomass was evaluated in terms of lipid recovery rate, total carbohydrate content, fatty acid composition, and thermal chemical behavior of biomass. Results indicated that, lipid recovery rate was increased from 52.03% of untreated biomass to 80.90%, 66.92%, and 75.26% of the biomass treated by aCh-O, aCh-EG and aU-A, respectively. However, there were no major changes observed in fatty acid profiles of both untreated and treated biomass, specifically palmitic acid, palmitoleic acid and stearic acid under various pretreatments. Furthermore, characterizations of untreated and treated biomass were carried out using Fourier transform infrared (FTIR), thermogravimetry analysis (TGA) and scanning electron microscope (SEM) to understand the enhanced lipids recovery. [ABSTRACT FROM AUTHOR]

Amphora subtropica and Dunaliella sp. isolated from Tunisian biotopes were retained for their high lipid contents. Respective optimized parameters for rapid growth were: pH 9 and 10, light period 21 and 24 h and temperature 31 and 34 °C, respectively. After optimization, Amphora subtropica growth rate increased from 0.2 to 0.5 day −1 and Dunaliella sp. growth rate increased from 0.38 to 0.7 day −1 . Amphora subtropica biomass production, productivity and lipid content increased from 0.3 to 0.7 g L −1 (dw), 69–100 mg L −1 d −1 (dw) and 150–190 g kg −1 (dw), respectively, and Dunaliella sp. from 0.5 to 1.4 g L −1 (dw), 124–200 mg L −1 d −1 (dw) and 190–280 g kg −1 (dw), respectively. Often to overcome trade-off between microalgae rapid growth and high lipid content which are often conflicting and very difficult to obtain at the same time, separation in a growth stage and a lipid accumulation stage is obvious. Salinity stress in a single stage of culture was studied. Compared to the optimal concentration of growth, excess or deficiency of NaCl engendered the same cellular responses by implication of oxidative stress systems and reactivation of defense and storage systems. Indeed, increasing salinity from 1 M to 2 M for Amphora subtropica or decreasing salinity from 3 M to 2 M for Dunaliella sp. have both increased lipids content from (220 and 280) to (350 and 430) g kg −1 , carotenoids from (1.8 and 2.4) to (2.3 and 3.7) pg cell −1 , TBARS amount from (10.4 and 5.3) to (12.1 and 10.7) nmol mg −1 proteins and SOD activity from of (46.6 and 61.8) to (71.6 and 79.4) U mg −1 proteins, respectively. With further improved fatty acids profile, the microalgae strains could be potent candidates for biofuel production. [ABSTRACT FROM AUTHOR]

Crude glycerol (byproduct of biodiesel preparation) was utilised as the carbon source to produce lipid using oleaginous yeast Rhodosporidium toruloides 32489. Under the same conditions, lipid production with crude glycerol was higher than those produced with glucose and pure glycerol. The effects of 4 main impurities in crude glycerol (methyl oleate, sodium oleate, NaCl and methanol) on lipid production were investigated. Compared with utilising pure glycerol, addition of methyl oleate, sodium oleate, and NaCl impurities increased lipid production by 47.0%, 68.0% and 64.0%, respectively, while methanol decreased lipid production by 17.7%. However, when methanol was mixed with other impurities, its inhibition effect was alleviated due to the promoting effect of other impurities. Hence, crude glycerol could be used as a renewable and low-cost carbon source to replace pure glucose or glycerol for lipid preparation. [ABSTRACT FROM AUTHOR]

Cultivation modes of autotrophic microalgae for biodiesel production utilizing open raceway pond were analyzed in this study. Five before screened good microalgae were tested their lipid productivity and biodiesel quality again in outdoor 1000 L ORP. Then, Chlorella sp. L1 and Monoraphidium dybowskii Y2 were selected due to their stronger environmental adaptability, higher lipid productivity and better biodiesel properties. Further scale up cultivation for two species with batch and semi-continuous culture was conducted. In 40,000 L ORP, higher lipid productivity (5.15 versus 4.06 g m −2 d −1 for Chlorella sp. L1, 5.35 versus 3.00 g m −2 d −1 for M . dybowskii Y2) was achieved in semi-continuous mode. Moreover, the financial costs of 14.18 $ gal −1 and 13.31 $ gal −1 for crude biodiesel in two microalgae with semi-continuous mode were more economically feasible for commercial production on large scale outdoors. [ABSTRACT FROM AUTHOR]

The aim of the present work was to develop a mathematical model to describe the biomass and (total) lipid productivity of Chlorella pyrenoidosa NCIM 2738 under heterotrophic conditions. Biomass growth rate was predicted by Droop’s cell quota model, while changes observed in cell quota (utilization) under carbon excess conditions were used for the modeling and predicting the lipid accumulation rate. The model was simulated under non-limiting (excess) carbon and limiting nitrate concentration and validated with experimental data for the culture grown in batch (flask) mode under different nitrate concentrations. The present model incorporated two modes (growth and stressed) for the prediction of endogenous lipid synthesis/induction and aimed to predict the effect and response of the microalgae under nutrient starvation (stressed) conditions. MATLAB and Genetic Algorithm were employed for the prediction and validation of the model parameters. [ABSTRACT FROM AUTHOR]

Strain selection is one of the primary hurdles facing cost-effective microalgal biodiesel production. Indeed, the strain used affects both upstream and downstream biodiesel production processes. This study presents a screening procedure that considers the most significant criteria in microalgal biodiesel production including TAG production and wet extraction and recovery of TAGs. Fourteen freshwater and seawater strains were investigated. Large variation was observed between the strains in all the screening criteria. The overall screening procedure ultimately led to the identification of Parachlorella kessleri UTEX2229 and Nannochloropsis gaditana CCMP527 as the best freshwater and seawater strains, respectively. They featured the largest areal TAG productivity equal to 2.7 × 10 −3 and 2.3 × 10 −3 kg m −2 d −1 , respectively. These two strains also displayed encouraging cell fragility in a high pressure bead milling process with 69% and 98% cell disruption at 1750 bar making them remarkable strains for TAG extraction in wet environment. [ABSTRACT FROM AUTHOR]

Single cell oil (SCO), promising as alternative oil source, was produced from steam exploded corn stover (SECS) by Mortierella isabellina . Different bioprocesses from SECS to SCO were compared and the bioprocess C using the three-stage enzymatic hydrolysis was found to be the most efficient one. The bioprocess C used the lowest enzyme input 20 FPIU cellulase/g glucan and the shortest time 222 h, but produced 44.94 g dry cell biomass and 25.77 g lipid from 327.63 g dry SECS. It had the highest lipid content 57.34%, and its productivities and yields were much higher than those of the bioprocess B and comparable to the bioprocess A, indicating that the three-stage enzymatic hydrolysis could greatly improve the efficiency of the bioprocess from high solid loading SECS to SCO by Mortierella isabellina . This work testified the application value of three-stage enzymatic hydrolysis in lignocellulose-based bioprocesses. [ABSTRACT FROM AUTHOR]

In order to obtain microalgal saponifiable lipids (SLs) fractions containing different polar lipid (glycolipids and phospholipids) contents, SLs were extracted from wet Nannochloropsis gaditana microalgal biomass using seven extraction systems, and the polar lipid contents of some fractions were reduced by low temperature acetone crystallization. We observed that the polar lipid content in the extracted lipids depended on the polarity of the first solvent used in the extraction system. Lipid fractions with polar lipid contents between 75.1% and 15.3% were obtained. Some of these fractions were transformed into fatty acid methyl esters (FAMEs, biodiesel) by methanolysis, catalyzed by the lipases Novozym 435 and Rhizopus oryzae in tert-butanol medium. We observed that the reaction velocity was higher the lower the polar lipid content, and that the final FAME conversions achieved after using the same lipase batch to catalyze consecutive reactions decreased in relation to an increase in the polar lipid content. [ABSTRACT FROM AUTHOR]

Coelastrella sp. QY01, a microalgae species isolated from a local pond, was identified and used for the treatment of anaerobically and aerobically treated swine wastewater (AnATSW). Microalgal growth characteristics, nutrient removal and lipid accumulation of QY01 cultivated in the initial concentration of AnATSW ranged from 63 to 319 mg NH 3 -N/L were examined. The specific growth rate of QY01 cultivated in cultures ranged from 0.269 to 0.325 day −1 with a biomass productivity from 42.77 to 57.46 mg L −1 day −1 . Removal rates for NH 3 -N, TP and inorganic carbon in AnATSW at the various nutrient concentrations ranged from 90% to 100%, from 90% to 100% and from 74% to 78%, respectively. The lipid content of QY01 ranged from 22.4% to 24.8%. The lipid productivity was positive correlation with the biomass productivity. 40% AnATSW was optimal for QY01 cultivation, in which nutrient removal and productivity of biomass and lipid were maximized. [ABSTRACT FROM AUTHOR]

During the study of Trentepohlia arborum it became clear that its cells are rich in lipids and carotenoids. Thus, lipid content, composition and fatty acids profiles in individual lipid classes, as well as pigment profiles, responding to different culture conditions, were further investigated. The results showed that the predominant carotenoids and lipid fraction in total lipid in this study was β -carotene and TAG, respectively. The lipid content increased significantly under high light while nitrogen-replete conditions induced the highest carotenoids content. However, only with a double stress of high light and nitrogen-deficiency it was possible to maximize the productivities of both carotenoids and lipids. Carotenoids (mainly β -carotene) accounted for ca . 5% of the microalgal lipid under the double stress. Data herein show the potential of T. arborum for the production of both lipids and carotenoids, and hence provide an appropriate way to produce different products from T. arborum . [ABSTRACT FROM AUTHOR]

This study evaluated the suitability of pinewood pyrolysates as a carbon source for lipid production and cultivation of the oleaginous yeast Rhodosporidium diobovatum and the microalgae Chlorella vulgaris . Thermal decomposition of pinewood and fractional condensation were used to obtain an oil rich in levoglucosan which was upgraded to glucose by acid hydrolysis. Blending of pyrolytic sugars with pure glucose in both nitrogen rich and nitrogen limited conditions was studied for R. diobovatum , and under nitrogen limited conditions for C. vulgaris . Glucose consumption rate decreased with increasing proportions of pyrolytic sugars increasing cultivation time. While R. diobovatum was capable of growth in 100% (v/v) pyrolytic sugars, C. vulgaris growth declined rapidly in blends greater than 20% (v/v) until no growth was detected in blends >40%. Finally, the effects of pyrolysis sugars on lipid composition was evaluated and biodiesel fuel properties were estimated based on the lipid profiles. [ABSTRACT FROM AUTHOR]

Mixotrophic growth of microalgae to boost lipid production is currently under active investigation. Such a process could be of practical importance if a cheap source of organic carbon, such as waste glycerol from biodiesel production, could be used. Several previous studies have already demonstrated that this carbon source can be used by different indigenous strains of microalgae. In this study it is shown that different nitrogen limitation strategies can be applied to further increase lipid production during growth with glycerol. In one strategy, cultures were grown in nitrogen replete medium and then resuspended in nitrogen free medium. In a second strategy, cultures were grown with different initial concentrations of nitrate. Lipid production by the two microalgal strains used, Chlorella sorokiniana (PCH02) and Chlorella vulgaris (PCH05), was shown to be boosted by strategies of nitrogen limitation, but they responded differently to how nitrogen limitation was imposed. [ABSTRACT FROM AUTHOR]

Municipal wastewater sludge is a promising lipid feedstock for biodiesel production, but the need to eliminate the high water content before lipid extraction is the main limitation for scaling up. This study evaluates the economic feasibility of biodiesel production directly from liquid primary sludge based on experimental data at laboratory scale. Computational tools were used for the modelling of the process scale-up and the different configurations of lipid extraction to optimise this step, as it is the most expensive. The operational variables with a major influence in the cost were the extraction time and the amount of solvent. The optimised extraction process had a break-even price of biodiesel of 1232 $/t, being economically competitive with the current cost of fossil diesel. The proposed biodiesel production process from waste sludge eliminates the expensive step of sludge drying, lowering the biodiesel price. [ABSTRACT FROM AUTHOR]

High moisture content in wet algal biomass hinders effective performance of current lipid extraction methods. An improved aqueous extraction method combing thermal and enzymatic lysis was proposed and performed in algal slurry of Nannochloropsis oceanica (96.0% moisture) in this study. In general, cell-wall of N. oceanica was disrupted via thermal lysis and enzymatic lysis and lipid extraction was performed using aqueous surfactant solution. At the optimal conditions, high extraction efficiencies for both lipid (88.3%) and protein (62.4%) were obtained, which were significantly higher than those of traditional hexane extraction and other methods for wet algal biomass. Furthermore, an excessive extraction of polar lipid was found for wet biomass compared with dry biomass. The advantage of this method is to efficiently extract lipids from high moisture content algal biomass and avoid using organic solvent, indicating immense potential for commercial microalgae-based biofuel production. [ABSTRACT FROM AUTHOR]

A mixed culture of microalgae, containing two Scenedesmus species, was analysed to determine its potential in coupling of pulp and paper mill effluent treatment and microalgal cultivation. Laboratory studies suggested that 60% concentration of wastewater was optimum for microalgal cultivation. A maximum of 82% and 75% removal of BOD and COD respectively was achieved with microalgal cultivation in outdoor open pond. By the end of the cultivation period, 65% removal of NO 3 -N and 71.29% removal of PO 4 -P was observed. The fatty acid composition of mixed microalgal culture cultivated with effluent showed the palmitic acid, oleic acid, linoleic acid and α-linolenic acid as major fatty acids. The results obtained suggest that pulp and paper mill effluent could be used effectively for cultivation of microalgae to minimise the freshwater and nutrient requirements. [ABSTRACT FROM AUTHOR]

To understand in which way the structural differences of three marine microalgae ( Nannochloropsis gaditana , Rhodomonas marina and Isochrysis sp.) affect their carbon partitioning, growth and applicability; a stoichiometric imbalance was imposed by steady carbon and other nutrients variation. Towards high nutrients concentrations/low carbon availability a decrease of 12–51% in C/N microalgae ratio was observed and maximum cell densities were achieved. Moreover, linear correlation between the nutrient input and microalgae protein content were observed. The macromolecular ratios pointed that carbohydrate was the main contributor for the C/N decrement. Although lipid content in R. marina remained constant throughout the experiment, a rise of 37–107% in N. gaditana and Isochrysis sp. was verified. Lipid fractions revealed high percentages of glycolipids in all microalgae (57–73% of total lipids). The present study shows an easy way to understand and modulate microalgae carbon partitioning relying on the field of application. [ABSTRACT FROM AUTHOR]

This study evaluated the suitability of pinewood pyrolysates as a carbon source for lipid production and cultivation of the oleaginous yeast Rhodosporidium diobovatum and the microalgae Chlorella vulgaris . Thermal decomposition of pinewood and fractional condensation were used to obtain an oil rich in levoglucosan which was upgraded to glucose by acid hydrolysis. Blending of pyrolytic sugars with pure glucose in both nitrogen rich and nitrogen limited conditions was studied for R. diobovatum , and under nitrogen limited conditions for C. vulgaris . Glucose consumption rate decreased with increasing proportions of pyrolytic sugars increasing cultivation time. While R. diobovatum was capable of growth in 100% (v/v) pyrolytic sugars, C. vulgaris growth declined rapidly in blends greater than 20% (v/v) until no growth was detected in blends >40%. Finally, the effects of pyrolysis sugars on lipid composition was evaluated and biodiesel fuel properties were estimated based on the lipid profiles. [ABSTRACT FROM AUTHOR]

Biomass productivity and growth kinetics for microalgae grown on sodium bicarbonate and diammonium phosphate were investigated. Different carbon and nitrogen ratios have shown different growth rates and biomass productivity and C:N ratio 50:10 as mg L −1 has shown the best production than all. For effective lipids extraction from biomass thermolysis and sonolysis were carried out from wet biomass. Sonolysis at 2.3 W intensity for 5 min has released 8.58 mg at neutral pH. More quantity of lipids was extracted when extraction was made at pH 4 and 10 which resulted 9 mg and 9.28 mg lipids respectively. Thermal treatment at 100 °C for 10 min has released 12.82 mg lipid at neutral pH. In the same thermolysis at pH 4 and 10 more quantity of lipids was extracted which were 15.16 mg and 14.81 mg respectively. Finally transesterified lipids were analyzed through GC–MS for FAME composition analysis. [ABSTRACT FROM AUTHOR]

Paper mill sludge (PMS) was assessed as cheap renewable lignocellulosic biomass for lipid production by the oleaginous yeast Cryptococcus vishniaccii (MTCC 232). The sonicated paper mill sludge extract (PMSE) exhibited enhanced lipid yield and lipid content 7.8 ± 0.57 g/l, 53.40% in comparison to 5.5 ± 0.8 g/l, 40.44% glucose synthetic medium, respectively. The accumulated triglycerides (TAG) inside the lipid droplets (LDs) were converted to biodiesel by transesterification and thoroughly characterized using GC–MS technique. The fatty acid methyl ester (FAME) profile obtained reveals elevated content of oleic acid followed by palmitic acid, linoleic acid and stearic acid with improved oxidative stability related to biodiesel quality. [ABSTRACT FROM AUTHOR]

Cell disruption by bead milling of Neochloris oleoabundans grown under nitrogen repleted (NR) and nitrogen depleted (ND) conditions was evaluated based on the release of biochemicals and biomass to the supernatant. Additionally, energy consumption for cell disruption was calculated per kg of released component. Bead milling of NR cells resulted on average in 34% (w/w) release of biochemicals into the supernatant, with a similar composition as the untreated microalgal biomass. With ND cells, the release was higher and more selective, i.e. 57%, 59%, 68% and 56% (w/w) of respectively biomass, proteins, carbohydrates and lipids whereof 92%, 57% and 46% (w/w) respectively of phospho-, glyco- and neutral lipids. [ABSTRACT FROM AUTHOR]

Municipal wastewater sludge is a promising lipid feedstock for biodiesel production, but the need to eliminate the high water content before lipid extraction is the main limitation for scaling up. This study evaluates the economic feasibility of biodiesel production directly from liquid primary sludge based on experimental data at laboratory scale. Computational tools were used for the modelling of the process scale-up and the different configurations of lipid extraction to optimise this step, as it is the most expensive. The operational variables with a major influence in the cost were the extraction time and the amount of solvent. The optimised extraction process had a break-even price of biodiesel of 1232 $/t, being economically competitive with the current cost of fossil diesel. The proposed biodiesel production process from waste sludge eliminates the expensive step of sludge drying, lowering the biodiesel price. [ABSTRACT FROM AUTHOR]

High moisture content in wet algal biomass hinders effective performance of current lipid extraction methods. An improved aqueous extraction method combing thermal and enzymatic lysis was proposed and performed in algal slurry of Nannochloropsis oceanica (96.0% moisture) in this study. In general, cell-wall of N. oceanica was disrupted via thermal lysis and enzymatic lysis and lipid extraction was performed using aqueous surfactant solution. At the optimal conditions, high extraction efficiencies for both lipid (88.3%) and protein (62.4%) were obtained, which were significantly higher than those of traditional hexane extraction and other methods for wet algal biomass. Furthermore, an excessive extraction of polar lipid was found for wet biomass compared with dry biomass. The advantage of this method is to efficiently extract lipids from high moisture content algal biomass and avoid using organic solvent, indicating immense potential for commercial microalgae-based biofuel production. [ABSTRACT FROM AUTHOR]

A mixed culture of microalgae, containing two Scenedesmus species, was analysed to determine its potential in coupling of pulp and paper mill effluent treatment and microalgal cultivation. Laboratory studies suggested that 60% concentration of wastewater was optimum for microalgal cultivation. A maximum of 82% and 75% removal of BOD and COD respectively was achieved with microalgal cultivation in outdoor open pond. By the end of the cultivation period, 65% removal of NO 3 -N and 71.29% removal of PO 4 -P was observed. The fatty acid composition of mixed microalgal culture cultivated with effluent showed the palmitic acid, oleic acid, linoleic acid and α-linolenic acid as major fatty acids. The results obtained suggest that pulp and paper mill effluent could be used effectively for cultivation of microalgae to minimise the freshwater and nutrient requirements. [ABSTRACT FROM AUTHOR]

This study fundamentally investigated the pseudo-catalytic transesterification of dried Nannochloropsis oceanica into fatty acid methyl esters (FAMEs) without oil extraction, which was achieved in less than 5 min via a thermo-chemical pathway. This study presented that the pseudo-catalytic transesterification reaction was achieved in the presence of silica and that its main driving force was identified as temperature: pores in silica provided the numerous reaction space like a micro-reactor, where the heterogeneous reaction was developed. The introduced FAME derivatization showed an extraordinarily high tolerance of impurities ( i.e ., pyrolytic products and various extractives). This study also explored the thermal cracking of FAMEs derived from N. oceanica : the thermal cracking of saturated FAMEs was invulnerable at temperatures lower than 400 °C. Lastly, this study reported that N. oceanica contained 14.4 wt.% of dried N. oceanica and that the introduced methylation technique could be applicable to many research fields sharing the transesterification platform. [ABSTRACT FROM AUTHOR]

A novel culture medium to enhance the biomass and lipid production simultaneously by Chlorella vulgaris UTEX 26 was designed in three stages of optimization. Initially, a culture medium was inferred applying the response surface method to adjust six factors [NaNO 3 , NH 4 HCO 3 , MgSO 4 ·7H 2 O, KH 2 PO 4 , K 2 HPO 4 and (NH 4 ) 2 HPO 4 ], which were selected on the basement of BBM (Bold’s Basal Medium) and HAMGM (Highly Assimilable Minimal Growth Medium) culture media. Afterwards, the nitrogen source compound was optimized to reduce both, ammonium and nitrate concentrations. As result of the optimization process, the proposed culture medium improved 40% the biomass (0.73 g L −1 ) compared with the BBM medium and 85% the lipid concentration (281 mg L −1 ), with respect to HAMGM medium. Some culture media components concentrations were reduced up to 50%. Gas chromatography analysis revealed that C16:0, C18:0, C18:1, C18:2 and C18:3 were the major fatty acids produced by C. vulgaris UTEX 26. [ABSTRACT FROM AUTHOR]

Conditions of light-emitting diode (LED) wavelength, light intensity, nitrate concentration, and time of exposure to green LED light stress in a two-phase culture were optimized for lipid production with three species of microalgae. Among the three microalgae, Nannochloropsis oculata showed the highest specific growth rate ( μ max ) of 0.037 h −1 and the lowest saturation constant ( K s ) of 1.32 mg/L. The highest lipid contents of the three microalgae in the second phase under green LED light stress were 52.0% (w/w) for Nannochloropsis salina at 2 days, 53.0% (w/w) for Nannochloropsis oceanica at 2 days, and 56.0% for N. oculata at 2 days. Fatty acid analysis of the microalgae showed that 85–87% (w/w) of total fatty acids from N. salina , N. oceanica , and N. oculata consisted of palmitic acid (C16:0) and oleic acid (C18:1). [ABSTRACT FROM AUTHOR]

A statistical mixture design approach was used to investigate the effects of cell wall degrading enzymes on the recovery of lipids from Nannochloropsis sp. A preliminary screening of potentially suitable enzyme preparations, including lysozyme, cellulase and different types of hemicellulases, was carried out. The most effective preparations were then taken as basic components for the formulation of enzyme mixtures. Optimized ternary mixtures consisting of cellulase and two hemicellulases were obtained which allowed the recovery of up to 37.2 g of lipids per 100 g of dry biomass. SEM and TEM images of the enzymatically treated microalga revealed extensive cell damage, with degradation of the cell wall and release of intracellular material. Overall, the results obtained demonstrate that the mixture design method can be used to prepare cell wall degrading enzyme cocktails that can significantly improve the recovery of lipids or other valuable components from microalgae. [ABSTRACT FROM AUTHOR]