Abstract Mixotrophic cultivation of Chlorella protothecoides was carried out in this study with an artificial light source. The culturing medium was supplemented with crude glycerol by-product from a biodiesel facility as an organic carbon source, and the spent yeast from a local brewery was used as an organic nitrogen source. Experiments were performed based on a 3×3 factorial design, with algal biomass (g/L) as the response. Data was fitted into a response surface model to investigate the impact on biomass of 3 factors: light intensity, carbon concentration and nitrogen concentration. According to the model, a maximal biomass of 20.94 g/L could be reached at a light intensity of 100 µmol m− 2s− 1, carbon concentration of 24.1 g/L and nitrogen concentration of 0.7 g/L.

Pretreatments are often needed for lignocellulosic biomass feedstocks before either thermochemical or biochemical conversion processes. Our previous research has demonstrated the potential of bioleaching, with its superior capability of removing certain inorganic compounds compared to water leaching, to improve biomass quality for thermochemical conversion in biofuel production. In this study, the bioleaching process was scaled up from 250 mL beakers to be carried out in custom-designed 2.5 L bioreactors. The fungus Aspergillus niger was used in the bioreactors for leaching sorghum straw biomass with an initial ash content of 6.0%. The effects of three operating parameters on leaching efficiency (i.e., residual ash content) were extensively studied, including the fungal mass added to each reactor, leaching time, and glucose concentration in the starting liquid phase. Response surface methodology (RSM) was used for the experiment design. The results showed that the average residual ash content of the sorghum feedstock after bioleaching was significantly lower (3.63 ± 0.19%) than that of the ash content (4.72 ± 0.13%) after water leaching (p < 0.00001). Among the three parameters, glucose concentration in the starting liquid phase had the most significant effect on leaching effectiveness (p = 0.0079). Based on this outcome, subsequent bioleaching experiments yielded reductions in residual ash content to as low as 2.73%.

To respond to anthropogenic effects on the global climate system, higher education institutions are assessing and aiming to reduce their greenhouse gas emissions. The objective of this paper was to evaluate the carbon footprint of Clemson University’s campus using a streamlined life cycle assessment approach. The carbon footprint sets a baseline for source specific evaluation and future mitigation efforts at Clemson University. Greenhouse gas emission sources presented in this carbon footprint include steam generation, refrigerants, electricity generation, electricity life cycle, various forms of transportation, wastewater treatment, and paper usage. This case study describes the approach used to quantify each greenhouse gas emission source, and discusses data assumptions and life cycles phases included to improve carbon footprint comparison with other higher education institutions. Results show that Clemson University’s carbon footprint for 2014 is approximately 95,000 metric tons CO2-equivalent, and 4.4 metric tons CO2-equivalent per student. Scope 1 emissions accounted for about 19% of the carbon footprint, while Scope 2 and 3 emissions each contributed nearly 41%. The largest sources of greenhouse gas emissions were electricity generation (41%), automotive commuting (18%), and steam generation (16%). Electricity generation from coal was 29% of the electricity generation resource mix and accounted for three-quarters of Clemson University’s GHG emissions associated with electricity.

Agricultural residues and energy crops often contain high contents of alkali metals, chlorine, silica, and other elements that promote slagging, fouling, corrosion, and gas emission during thermochemical conversion (e.g., combustion and gasification). Water leaching is a common method, but not always effective to reduce such elements. Bioleaching by adding microbes to water leaching was introduced to leach cellulosic biomass in this study. Three microbial species including two fungi (Fusarium oxysporum and Aspergillus niger) and one bacterium (Burkholderia fungorum) were selected to leach four lignocellulosic feedstocks such as corn stover, wheat straw, switchgrass, and sorghum. Among three microbes, A. niger was found the most efficient to remove most elements by 80% in 48 h, and sorghum was relatively more amenable to bioleaching. With A. niger, the bioleaching with water to feedstock (w/w) ratio of 25 for 6 h was sufficient to leach K (85%), Cl (90%), Mg (60%), and P (70%) from sorghum. Overall, bioleaching is more efficient than water leaching except for Na. Studies on bioleaching mechanism indicated that the acidification resulted from organic acids produced by A. niger during bioleaching might contribute to the higher leaching efficiency over other microbial species and water leaching.

Eversa Transform was used as an enzymatic catalyst to transform glandless and crude (heavy pigment) cottonseed oils into biodiesel. The oils were reacted with methanol at a 6: 1 molar ratio with modified amounts of water, lipase, and temperature. Reactions were conducted in the presence of lipase and water at doses of 2, 5, and 8 wt% and 1, 3, and 6 wt%, respectively. Product composition and conversion were determined using the gas chromatography method of ASTM D6584. Oxidative stability was determined following EN 15751. The conversion to fatty acid methyl esters averaged 98.5% across all samples. Temperature had the most significant effect on conversion (p < 0.0035). Lipase and water dosages did not affect conversion, while each had an effect with temperature that was significant across the difference between 3 and 1 wt% water content and between 8 and 5 wt% enzyme content between the two temperatures (p = 0.0018 and 0.0153), respectively. Induction periods (oxidative stability) of the glandless and crude cottonseed oils were significantly different, but there was no difference between the two oil conversions based on oil type.

Biodiesel from waste cooking oil (WCO) requires antioxidants to meet oxidation stability specifications set forth in ASTM D6751 or EN 14214. In contrast, unrefined cottonseed oil (CSO), containing tocopherols and gossypol, produces biodiesel of higher oxidation stability. However, only a portion of these CSO endogenous antioxidants are suspected to be retained in biodiesel. Because the economics of biodiesel manufacturing rely upon inexpensive sources of triglycerides, emphasis was placed on developing improved alternative processing methods where WCO was the main source of methyl esters (WCOME) and CSO was used as a supplemental source of triglycerides and antioxidants in a 4:1 ratio. This study compared four processing methods for their ability to produce biodiesel of increased oxidative stability prepared from a 4:1 ratio of WCO:CSO. Two novel processing methods developed for this study utilise solvent properties of fatty acid methyl esters and glycerol to avoid additional chemical inventory for biodiesel processors. This study concludes that the two new processing methods resulted in biodiesel that had statistically significant improved oxidation stability when compared to two common industrial processing methods. Another significant finding is that high-shear homogenisation during transesterification reduced reaction time from the published one hour to 16 minutes.

Microalga is a promising feedstock for biofuel, chemical, food, and animal feed; however, harvesting is a critical barrier for its commercial application. This communication demonstrates a new harvesting technology by utilizing the phase separation of thermoresponsive polymers and charged copolymers of N-isopropylacrylamide and allylamine. Chlorella protothecoides cells are separated from solution when the mixture of algae and polymers is heated above the lower critical solution temperature of polymers (~ 32 °C), where the polymer phase separates from the aqueous media and aggregates into a solid–gel phase. It was found that copolymer concentration, allylamine content (mol%) and charge (based on initial solution pH) affect the extent of polymer phase separation and alga separation efficiency. The copolymer containing allylamine with lower than 2.6 mol% displayed nearly complete algal cell separation at polymer concentrations of 25–50 mg/mL and pH 7. The results indicated that thermoresponsive polymers provide a promising technology for alga harvesting using recyclable and reusable materials.

Biomass and lipid accumulation of heterotrophic microalgae Chlorella protothecoides by supplying mixed waste substrate of brewer fermentation and crude glycerol were investigated. The biomass concentrations of the old and the new C. protothecoides strains on day 6 reached 14.07 and 12.73 g/L, respectively, which were comparable to those in basal medium with supplement of glucose and yeast extract (BM-GY) (14.47 g/L for old strains and 11.43 g/L for new strains) (P>0.05). Approximately 81.5% of total organic carbon and 65.1% of total nitrogen in the mixed waste were effectively removed. The accumulated lipid productivities of the old and the new C. protothecoides strains in BM-GY were 2.07 and 1.61 g/L/day, respectively, whereas in the mixed waste, lipid productivities could reach 2.12 and 1.81 g/L/day, respectively. Our result highlights a new approach of mixing carbon-rich and nitrogen-rich wastes as economical and practical alternative substrates for biofuel production.

An integrated process has been developed for a sweet sorghum (Sorghum bicolor (L.) Moench) biorefinery in which all carbohydrate components of the feestock are used for production of fuel ethanol and industrial chemicals. In the first step, the juice is extracted from the stalks. The resulted straw (bagasse) then is pretreated using the soaking in aqueous ammonia (SAA) process, which does not result in significant loss of hemicellulose, to enhance subsequent enzyme hydrolysis for production of fermentable sugars. Following pretreatment the straw is hydrolyzed first with commercial enzyme product containing high hemicellulase activity (Accellerase XY). The xylose-rich solution obtained after solid/liquid separation is used for production of value-added co-products using suitable microorganisms. The value-added co-products produced to demonstrate the feasibility include astaxanthin and D-ribose. The residual solids then are hydrolyzed with commercial enzyme product containing high cellulase activity (Accellerase 1500) with the juice extracted in the first step being used as make-up water. By combining the sugar in the juice with the glucose released from the residual solids by enzyme hydrolysis high ethanol concentrations can be achieved, which results in lower distillation cost than if pure water is used for enzyme hydrolysis and subsequent fermentation as normally performed in cellulosic ethanol production.

Lipids obtained from Chlorella protothecoides in heterotrophic cultivation are considered a suitable feedstock for biodiesel production. In this study, glucose fed-batch fermentation was performed to increase final biomass and lipid production. The biomass productivity and lipid productivity were 6.28 and 2.06 g/L day, respectively. Biomass/glucose conversion and the lipid/glucose conversion were 43.3% and 14.2%, respectively. Extraction of lipids from algae has been identified as a key bottleneck in bioprocessing operations. Supercritical carbon dioxide (SC-CO(2)) was applied for neutral lipids extraction and the SC-CO(2) kinetics was investigated by the Goto et al. model. The modeling showed a good fit with experimental data. Additionally, neutral lipids extracted by SC-CO(2) displayed a suitable fatty acid profile for biodiesel [mainly C18:1 (60.0%), C18:2 (18.7%) and C16:0 (11.5%)]. Our study demonstrated the ability to produce high levels of neutral lipids through heterotrophic algal culture and subsequent extraction of lipids with SC-CO(2) method developed.

Transesterification of refined cottonseed oil (CSO) was carried out with methanol, ethanol, 1-butanol, and various mixtures of these alcohols to produce biodiesel. In the mixed alcohol transesterifications, formation of methyl esters was favored over ethyl and butyl esters. The influence of ester head group on fuel properties was determined. Specifically, cold flow properties, lubricity, and energy content improved in the order: CSO butyl esters (CSBE, best) > ethyl esters (CSEE) > methyl esters (CSME). Higher kinematic viscosities (KVs) as well as lower iodine values (IVs) and wear scars were observed with larger ester head groups. Blends of CSME, CSEE and CSBE exhibited properties intermediate to the neat esters. All ester samples were within the limits prescribed in ASTM D6751 and EN 14214 for cetane number, acid value (AV), glycerol (free and total) content, sulfur, and phosphorous. Also examined was the influence of blending alkyl esters with petrodiesel. All blends exhibited improved cold flow properties versus unblended alkyl esters. Enhanced lubricity was observed after blending. With increasing content of biodiesel, higher KVs and lower energy contents were observed. Finally, all blends were within the limits specified in ASTM D975 and D7467 for AV, KV and sulfur.

Biodiesel, defined as mono-alkyl esters of long-chain fatty acids derived from vegetable oils or animal fats, is an attractive renewable fuel alternative to conventional petroleum diesel fuel. Biodiesel produced from oils such as cottonseed oil and poultry fats suffer from extremely poor cold flow properties because of their high saturated fatty acid content. In the current study, Ethyl Levulinate (ethyl 4-oxopentanoate) was investigated as a novel, bio-based cold flow improver for use in biodiesel fuels. The cloud (CP), pour (PP), and cold filter plugging points (CFPP) of biodiesel fuels prepared from cottonseed oil and poultry fat were improved upon addition of ethyl levulinate at 2.5, 5.0, 10.0, and 20.0% (vol). Reductions of 4-5 degrees C in CP, 3-4 degrees C in PP and 3 degrees C in CFPP were observed at 20 vol % ethyl levulinate. The influence of ethyl levulinate on acid value, induction period, kinematic viscosity and flash point was determined. The kinematic viscosities and flash points decreased with increasing content of ethyl levulinate. All samples (<= 15 vol % ethyl levulinate) satisfied the ASTM D6751 limit with respect to flash point, but none of the 20 vol % blends were acceptable when compared to the higher EN 14214 specification. Acid value and oxidative stability were essentially unchanged upon addition of ethyl levulinate. In summary, ethyl levulinate appears acceptable as a diluent for biodiesel fuels with high saturated fatty acid content. (C) 2011 Published by Elsevier Ltd.

Objective: Accumulating evidence in both humans and animal models indicates that dietary intake of long-chain polyunsaturated fatty acids (PUFAs) can improve response to chemotherapy. The intent of this study was to determine the mechanisms by which PUFAs affect the response to anticancer chemotherapy. Methods: Human colorectal cancer cell line Caco-2 was used as a model system in this study. Caco-2 cells were treated with different concentrations of three PUFAs: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA). Real-time polymerase chain reaction was used to determine mdr1 gene (codes for P-glycoprotein [P-gp]) expression. Western blotting and calcein-acetoxymethylester efflux assay were used for P-gp expression and functional evaluation, respectively. Furthermore, apoptosis assay was conducted by adding PUFAs with paclitaxel to confirm the synergetic effect. Finally, gene expression of nuclear receptors CAR and PXR were estimated to evaluate the possible mechanisms. Results: Both classes of PUFAs, omega-3 (ω-3) and omega-6 (ω-6), can cause a modest but very reproducible reduction of gene expression, protein production, and pump activity of MDR1. Incubation of cells with PUFAs greatly enhanced the cytotoxicity of the anticancer drug paclitaxel, manifested mainly through enhanced paclitaxel-induced apoptosis. Furthermore, PUFAs increased the messenger RNA (mRNA) levels of the nuclear receptors CAR and PXR, thus implicating these two transcription factors as cellular targets of PUFAs in cells but not directly affecting MDR1 regulation. Conclusions: Our results suggest that inhibition of the multidrug resistance MDR1/P-gp is one mechanism through which dietary polyunsaturated fatty acids exert a synergetic effect on the response of tumor cells to anticancer drugs.

Microalgal lipids may be a more sustainable biodiesel feedstock than crop oils. We have investigated the potential for using the crude glycerol as a carbon substrate. In batch mode, the biomass and lipid concentration of Chlorella protothecoides cultivated in a crude glycerol medium were, respectively, 23.5 and 14.6 g/l in a 6-day cultivation. In the fed-batch mode, the biomass and lipid concentration improved to 45.2 and 24.6 g/l after 8.2 days of cultivation, respectively. The maximum lipid productivity of 3 g/l day in the fed-batch mode was higher than that produced by batch cultivation. This work demonstrates the feasibility of crude biodiesel glycerol as an alternative carbon substrate to glucose for microalgal cultivation and a cost reduction of carbon substrate feed in microalgal lipid production may be expected.

The low temperature operability and oxidative stability of cottonseed oil methyl esters (CSME) were improved with four anti-gel additives as well as one antioxidant additive, gossypol. Low temperature operability and oxidative stability of CSME was determined by cloud point (CP), pour point (PP), cold filter plugging point (CFPP), and oxidative stability index (OSI). The most significant reductions in CP, PP, and CFPP in all cases were obtained with Technol (R), with the average reduction in temperature found to be 3.9 degrees C. Gunk (R), Heet (R), and Howe's (R) were progressively less effective, as indicated by average reductions in temperature of 3.4, 3.0, and 2.8 degrees C, respectively. In all cases, the magnitude of CFPP reduction was greater than for PP and especially CP. Addition of gossypol, a polyphenolic aldehyde, resulted in linear improvement in OSI (R-2 = 0.9804). The OSI of CSME increased from 5.0 to 8.3 h with gossypol at a concentration of 1000 ppm.