The use of Design of Experiments and Response Surface Methodology to optimize biomass and lipid production by the oleaginous marine green alga, Nannochloropsis gaditana in response to light intensity, inoculum size and CO2

Optimization of lipid production in Tetradesmus dimorphus using response surface methodology using tannery wastewater for biodiesel production

The management of industrial wastewaters and generation of sustainable energy resources are the two major challenges concerned with the global population and depleting fossil fuels. Tannery wastewater (TWW) is a major source of environmental pollution and human health hazardous if released without adequate treatment. The microalgal treatment of TWW among other approaches seems to be beneficial and effective as microalgae use TWW as nutrient source offering wastewater treatment while producing large biomass for biofuel production. Biomass and lipid content are the adequate criteria for higher biodiesel yield. In present study, Tetradesmus dimorphus was grown in TWW with an objective to treat TWW along with the generation of large biomass for biodiesel production and Response Surface Methodology (RSM) was used to optimize the biodiesel production taking into count the parameters such as wastewater concentrations, pH and photoperiod. Results showed that highest biomass and lipid content produced were 1.63 ± 0.02 g/L and 487 ± 11 mg/L, respectively with 213.80 ± 7 mg/L of biodiesel production. Gas Chromatography-Flame Ionization Detection (GC-FID) analysis of biodiesel obtained from Tetradesmus dimorphus lipids showed that it was made up of more than 40 % Methyl decanoate (C11:0) and Methyl erucate (C22:1). The interrelationships between selected parameters like STTWW concentrations, pH and photoperiods reflected the positive impact on lipid productivity as 3D contour depicted the maximum yield at 80 % wastewater concentration, pH 8 and 14 h of photoperiod. Study showed that microalgal treatment of TWW among the other approaches seems beneficial and effective to harness wastewater nutrients while producing valuable biomass for biodiesel production.

Bio-inspired multifunctional and reusable LiP@MFO-GO and LiP@MFO-Chit hybrid enzyme complexes for efficient degradation of melanin

Melanin is a complex brown pigment, primarily responsible for the skin pigmentation. Therefore, cosmetic industries have always been in search of potent oxidative enzymes useful for melanin degradation, and to promise a fair complexion after using their products. In the present study, lignin peroxidase from Pseudomonas fluorescence LiP-RL5 isolate has been immobilized on super-paramagnetic nanoparticles to enhance its stability and reusability. The chitosan coated enzyme-nanomaterial complex (LiP@MFO-Chit) showed higher melanin decolorization (47.30 ± 2.3 %) compared to the graphene oxide coated nanoparticles (LiP@MFO-GO) (41.60 ± 1.6 %). Synthesized enzyme nanoparticle complexes showed microbicidal effect on skin infection causing pathogen, Pantoea agglomerans with an inhibitory zone of 6.0 ± 0.9 mm and 250 µg/100 µl minimum inhibitory concentration, and a 7.0 ± 1.5 mm zone and 170 µg/100 µl MIC for LiP@MFO-GO and LiP@MFO-Chit, respectively. Antioxidant potential of LiP@MFO-Chit and LiP@MFO-GO nano-conjugates showed a substantial DPPH scavenging activity of 75.7 % and 88.3 %, respectively. Therefore, LiP-nanoparticle hybrid complexes analyzed in this study are not only effective as skin whitening agents but they are potential molecules against various microbial skin infections as well as useful for different other biomedical applications like biorefinery, drug delivery, and dermatology, etc.

Co-cultivation of microalgae and bacteria for optimal bioenergy feedstock production in wastewater by using response surface methodology

This work uses response surface methodology (RSM) to study the co-cultivation of symbiotic indigenous wastewater microalgae and bacteria under different conditions (inoculum ratio of bacteria to microalgae, CO2, light intensity, and harvest time) for optimal bioenergy feedstock production. The findings of this study demonstrate that the symbiotic microalgae-bacteria culture not only increases total microalgal biomass and lipid productivity, but also enlarges microalgal cell size and stimulates lipid accumulation. Meanwhile, inoculum ratio of bacteria to microalgae, light intensity, CO2, and harvest time significantly affect biomass and lipid productivity. CO2 concentration and harvest time have significant interactive effect on lipid productivity. The response of microalgal biomass and lipid productivity varies significantly from 2.1 × 105 to 1.9 × 107 cells/mL and 2.8 × 102 to 3.7 × 1012 Total Fluorescent Units/mL respectively. Conditions for optimum biomass and oil accumulation are 100% of inoculation ratio (bacteria/microalgae), 3.6% of CO2 (v/v), 205.8 µmol/m2/s of light intensity, and 10.6 days of harvest time. This work provides a systematic methodology with RSM to explore the benefits of symbiotic microalgae-bacteria culture, and to optimize various cultivation parameters within complex wastewater environments for practical applications of integrated wastewater-microalgae systems for cost-efficient bioenergy production.

Scenedesmus rubescens Heterotrophic Production Strategies for Added Value Biomass

Microalgae attract interest worldwide due to their potential for several applications. Scenedesmus is one of the first in vitro cultured algae due to their rapid growth and handling easiness. Within this genus, cells exhibit a highly resistant wall and propagate both auto- and heterotrophically. The main goal of the present work is to find scalable ways to produce a highly concentrated biomass of Scenedesmus rubescens in heterotrophic conditions. Scenedesmus rubescens growth was improved at the lab-scale by 3.2-fold (from 4.1 to 13 g/L of dry weight) through medium optimization by response surface methodology. Afterwards, scale-up was evaluated in 7 L stirred-tank reactor under fed-batch operation. Then, the optimized medium resulted in an overall productivity of 8.63 g/L/day and a maximum biomass concentration of 69.5 g/L. S. rubescens protein content achieved approximately 31% of dry weight, similar to the protein content of Chlorella vulgaris in heterotrophy.

Biomass and lipid production by the native green microalgae Chlorella sorokiniana in response to nutrients, light intensity, and carbon dioxide: experimental and modeling approach

Introduction: Microalgae are photosynthetic cells that can produce third-generation biofuels and other commercial compounds. Microalgal growth is influenced by two main parameters: light intensity and carbon dioxide concentration, which represent the energy and carbon source, respectively. For photosynthesis, the optimum values of abiotic factors vary among species. Methods: In this study, the microalga Chlorella sorokiniana was isolated from a freshwater lake. It was identified using molecular analysis of the ribosomal internal transcribed spacer. A single-factor design of experiments in 250-mL Erlenmeyer flasks was used to evaluate which concentrations of nitrogen and phosphorus increase the production of biomass and lipids. The response surface methodology was used with a 3²-factorial design (light intensity and CO₂ were used to evaluate its effect on biomass, lipid production, and specific growth rates, in 200-mL tubular photobioreactors (PBRs)). Results and Discussion: Low levels of light lead to lipid accumulation, while higher levels of light lead to the synthesis of cell biomass. The highest biomass and lipid production were 0.705 ± 0.04 g/L and 55.1% ± 4.1%, respectively. A mathematical model was proposed in order to describe the main phenomena occurring in the culture, such as oxygen and CO₂ mass transfer and the effect of light and nutrients on the growth of microalgae. The main novelties of this work were molecular identification of the strain, optimization of culture conditions for the indigenous microalgae species that were isolated, and formulation of a model that describes the behavior of the culture.

Integrating anaerobic digestion and microalgae cultivation for dairy wastewater treatment and potential biochemicals production from the harvested microalgal biomass

Utilizing wastewaters as feedstock for microalgal cultivation has the dual benefits of water-saving and low nutrient costs, with simultaneous remediation of pollutants and generation of value-added biochemical products. This study employed two different strategies to treat raw dairy wastewaters with moderate and high chemical oxygen demand (COD) levels. For moderate-COD dairy wastewater, the wastewater was directly utilized as feedstock for algal cultivation, in which the effects of wastewater dilution ratios and algal inoculum sizes were investigated. The results show that the microalga strain used (Chlorella sorokiniana SU-1) was capable of obtaining a high biomass concentration of 3.2 ± 0.1 g/L, accompanied by 86.8 ± 6%, 94.6 ± 3%, and 80.7 ± 1%, removal of COD, total phosphorus (TP) and total nitrogen (TN), respectively. Meanwhile, the obtained microalgal biomass has lipids content of up to 12.0 ± 0.7% at a wastewater dilution ratio of 50% and an inoculum size of 2 g/L. For high-COD dairy wastewater, an integrated process of anaerobic digestion and microalgal phycoremediation was employed, and the effect of inoculum sizes was also studied. The inoculum size of 2 g/L gave highest biomass production of 4.25 ± 0.10 g/L with over 93.0 ± 2.0% removal of COD, TP, and TN. The harvested microalgal biomass has lipids and protein content of 12.5 ± 2.2% and 18.0 ± 2.2%, respectively. The present study demonstrated potential microalgal phycoremediation strategies for the efficient COD removal and nutrients recovery from dairy wastewater of different COD levels with simultaneous production of microalgal biomass which contains valuable components, such as protein and lipids.

A Review on Synchronous Microalgal Lipid Enhancement and Wastewater Treatment

Microalgae are unicellular photosynthetic eukaryotes that can treat wastewater and provide us with biofuel. Microalgae cultivation utilizing wastewater is a promising approach for synchronous wastewater treatment and biofuel production. However, previous studies suggest that high microalgae biomass production reduces lipid production and vice versa. For cost-effective biofuel production from microalgae, synchronous lipid and biomass enhancement utilizing wastewater is necessary. Therefore, this study brings forth a comprehensive review of synchronous microalgal lipid and biomass enhancement strategies for biofuel production and wastewater treatment. The review emphasizes the appropriate synergy of the microalgae species, culture media, and synchronous lipid and biomass enhancement conditions as a sustainable, efficient solution.

The Great Capacity on Promoting Melanogenesis of Three Compatible Components in Vernonia anthelmintica (L.) Willd

To investigate a possible methodology of exploiting herbal medicine and design polytherapy for the treatment of skin depigmentation disorder, we have made use of Vernonia anthelmintica (L.) Willd., a traditional Chinese herbal medicine that has been proven to be effective in treating vitiligo. Here, we report that the extract of Vernonia anthelmintica (L.) Willd. effectively enhances melanogenesis responses in B16F10. In its compound library, we found three ingredients (butin, caffeic acid and luteolin) also have the activity of promoting melanogenesis in vivo and in vitro. They can reduce the accumulation of ROS induced by hydrogen peroxide and inflammatory response induced by sublethal concentrations of copper sulfate in wild type and green fluorescent protein (GFP)-labeled leukocytes zebrafish larvae. The overall objective of the present study aims to identify which compatibility proportions of the medicines may be more effective in promoting pigmentation. We utilized the D-optimal response surface methodology to optimize the ratio among three molecules. Combining three indicators of promoting melanogenesis, anti-inflammatory and antioxidant capacities, we get the best effect of butin, caffeic acid and luteolin at the ratio (butin:caffeic acid:luteolin = 7.38:28.30:64.32) on zebrafish. Moreover, the effect of melanin content recovery in the best combination is stronger than that of the monomer, which suggests that the three compounds have a synergistic effect on inducing melanogenesis. After simply verifying the result, we performed in situ hybridization on whole-mount zebrafish embryos to further explore the effects of multi-drugs combination on the proliferation and differentiation of melanocytes and the expression of genes (tyr, mitfa, dct, kit) related to melanin synthesis. In conclusion, the above three compatible compounds can significantly enhance melanogenesis and improve depigmentation in vivo.

Development of a novel nannochloropsis strain with enhanced violaxanthin yield for large-scale production

BACKGROUND

Nannochloropsis is a marine microalga that has been extensively studied. The major carotenoid produced by this group of microalgae is violaxanthin, which exhibits anti-inflammatory, anti-photoaging, and antiproliferative activities. Therefore, it has a wide range of potential applications. However, large-scale production of this pigment has not been much studied, thereby limiting its industrial application.

RESULTS

To develop a novel strain producing high amount of violaxanthin, various Nannochloropsis species were isolated from seawater samples and their violaxanthin production potential were compared. Of the strains tested, N. oceanica WS-1 exhibited the highest violaxanthin productivity; to further enhance the violaxanthin yield of WS-1, we performed gamma-ray-mediated random mutagenesis followed by colorimetric screening. As a result, Mutant M1 was selected because of its significant higher violaxanthin content and biomass productivity than WS-1 (5.21 ± 0.33 mg g^- 1 and 0.2101 g L^- 1 d^- 1, respectively). Subsequently, we employed a 10 L-scale bioreactor to confirm the large-scale production potential of M1, and the results indicated a 43.54 % increase in violaxanthin production compared with WS-1. In addition, comparative transcriptomic analysis performed under normal light condition identified possible mechanisms associated with remediating photo-inhibitory damage and other key responses in M1, which seemed to at least partially explain enhanced violaxanthin content and delayed growth.

CONCLUSIONS

Nannochloropsis oceanica mutant (M1) with enhanced violaxanthin content was developed and its physiological characteristics were investigated. In addition, enhanced production of violaxanthin was demonstrated in the large-scale cultivation. Key transcriptomic responses that are seemingly associated with different physiological responses of M1 were elucidated under normal light condition, the details of which would guide ongoing efforts to further maximize the industrial potential of violaxanthin producing strains.

Sexual Difference in the Optimum Environmental Conditions for Growth and Maturation of the Brown Alga Undaria pinnatifida in the Gametophyte Stage

Undaria pinnatifida is an annual brown kelp growing naturally in coastal areas as a major primary producer in temperate regions and is cultivated on an industrial scale. Kelps have a heteromorphic life cycle characterized by a macroscopic sporophyte and microscopic sexual gametophytes. The sex-dependent effects of different environmental factors on the growth and maturation characteristics of the gametophyte stage were investigated using response surface methodology. Gametophytes were taken from three sites in Japan: Iwate Prefecture, Tokushima Prefecture, and Kagoshima Prefecture in order to confirm the sexual differences in three independent lines. Optimum temperature and light intensity were higher for males (20.7-20.9 °C and 28.6-33.7 µmol m-2 s-1, respectively) than females (16.5-19.8 °C and 26.9-32.5 µmol m-2 s-1), and maturity progressed more quickly in males than females. Optimum wavelengths of light for growth and maturation of the gametophytes were observed for both blue (400-500 nm, λmax 453 nm) and green (500-600 nm; λmax 525 nm) lights and were sex-independent. These characteristics were consistent among the three regional lines. Slower growth optima and progress of maturation could be important for female gametophytes to restrict fertilization and sporophyte germination to the lower water temperatures of autumn and winter, and suggest that the female gametophyte may be more sensitive to temperature than the male. The sexual differences in sensitivity to environmental factors improved the synchronicity of sporeling production.

Steam co-gasification of horticultural waste and sewage sludge: Product distribution, synergistic analysis and optimization

In this study, horticultural waste (HW) and sewage sludge (SS) with different mass ratios were co-gasified with steam at different temperatures to investigate the product distribution, gas synergistic interaction, and optimal design for gas products from co-gasification process. Results showed that with the increase of SS ratio in blends, the H₂ content was increased and the syngas yield was decreased. The synergistic interaction was more significant at higher temperature which promoted the H₂ production probably due to the reduction and steam oxidation of Fe species in SS during co-gasification process. The optimized highest effective gas content (82.92 vol%) was achieved with the highest HHV (11.40 MJ/m³) at the conditions of SS ratio = 0.80 and temperature of 900 °C. It indicates that steam co-gasification of HW and SS is a promising technology to produce desired syngas towards a clean and efficient waste management process.

Consolidated bioprocessing of wastewater cocktail in an algal biorefinery for enhanced biomass, lipid and lutein production coupled with efficient CO2 capture: An advanced optimization approach

We present a holistic approach in establishing a successful green integrated bio-refinery system with improved biomass, lipid and lutein productivity, while remediating wastewater and sequestering CO₂ with potential biodiesel and healthcare applications. To achieve this we evaluated the effect of four process parameters: CO₂% supply; acetate concentration; poultry litter waste (PLW) concentration; and light intensity on cultivation of Chlorella minutissma following the Taguchi's design of experimental technique. A four factors, three levels orthogonal array was adopted to cultivate Chlorella minutissma in specially developed waste water medium. Effect of the process parameters on biomass productivity, CO₂ fixation rate, lipid content, lutein productivity and bioremediation capacity were determined. Results obtained from individual parametric combinations and Signal/Noise (S/N) ratio responses indicated S3 (5% CO₂, 100 mg L^-1 of acetate, 10 g L^-1 of poultry litter, and 15, 000 lux of light intensity) combination as the optimum cultivation condition. Following the S3 combination a significant enhancement in biomass productivity (292 mg L^-1 d^-1) with exceedingly high CO₂ fixation rate and photosynthetic efficiency (51.51 g L^-1 d^-1 of CO₂; P.E: 15.81%) was achieved. A maximum of 169.29 mg L^-1 d^-1 of lipid with a balanced distribution of saturated and unsaturated fatty acids conformed to the international standard for biodiesel was achieved. Additionally, 7.21 mg L^-1 d^-1 of lutein productivity was also accomplished within 7 day of cultivation, while remediating up to 93-90% of nitrogenous and phosphate substrates. Statistically, the results reinforced our findings with the S/N responses and experimental observations for a particular property.

Biomass and lipid induction strategies in microalgae for biofuel production and other applications

The use of fossil fuels has been strongly related to critical problems currently affecting society, such as: global warming, global greenhouse effects and pollution. These problems have affected the homeostasis of living organisms worldwide at an alarming rate. Due to this, it is imperative to look for alternatives to the use of fossil fuels and one of the relevant substitutes are biofuels. There are different types of biofuels (categories and generations) that have been previously explored, but recently, the use of microalgae has been strongly considered for the production of biofuels since they present a series of advantages over other biofuel production sources: (a) they don’t need arable land to grow and therefore do not compete with food crops (like biofuels produced from corn, sugar cane and other plants) and; (b) they exhibit rapid biomass production containing high oil contents, at least 15 to 20 times higher than land based oleaginous crops. Hence, these unicellular photosynthetic microorganisms have received great attention from researches to use them in the large-scale production of biofuels. However, one disadvantage of using microalgae is the high economic cost due to the low-yields of lipid content in the microalgae biomass. Thus, development of different methods to enhance microalgae biomass, as well as lipid content in the microalgae cells, would lead to the development of a sustainable low-cost process to produce biofuels. Within the last 10 years, many studies have reported different methods and strategies to induce lipid production to obtain higher lipid accumulation in the biomass of microalgae cells; however, there is not a comprehensive review in the literature that highlights, compares and discusses these strategies. Here, we review these strategies which include modulating light intensity in cultures, controlling and varying CO₂ levels and temperature, inducing nutrient starvation in the culture, the implementation of stress by incorporating heavy metal or inducing a high salinity condition, and the use of metabolic and genetic engineering techniques coupled with nanotechnology.

Mixotrophic Microalgae Biofilm: A Novel Algae Cultivation Strategy for Improved Productivity and Cost-efficiency of Biofuel Feedstock Production

In this work, we studied a novel algae cultivation strategy, mixotrophic microalgae biofilm, to improve the productivity and cost-efficiency of algal biofuel production. In contrast to previous methods, this improved approach can achieve high productivity at low cost by harnessing the benefits of mixotrophic growth’s high efficiency, i.e., capable of subsisting on inorganic and organic carbons thus unaffected by limited light, and microalgae biofilm’s low harvesting cost. Our results, as one of the first studies of this type, proved that microalgae biofilms under mixotrophic condition exhibited significantly higher productivity and quality of biofuel feedstock: 2–3 times higher of biomass yield, 2–10 times higher of lipid accumulation, and 40–60% lower of ash content when compared to microalgae biofilms under autotrophic condition. In addition, we investigated the impact of cell-surface properties (hydrophobicity and roughness) on the growth activities of microalgae biofilms and found that the productivity of mixotrophic biofilms was significantly correlated with the surface hydrophobicity. Finally, our work demonstrated the applicability of integrating this novel cultivation method with wastewater for maximum efficiency. This study opens a new possibility to solve the long-lasting challenges of algal biofuel feedstock production, i.e., low productivity and high cost of algal cultivation.

Optimization of multiplex quantitative polymerase chain reaction based on response surface methodology and an artificial neural network-genetic algorithm approach

Multiplex quantitative polymerase chain reaction (qPCR) has found an increasing range of applications. The construction of a reliable and dynamic mathematical model for multiplex qPCR that analyzes the effects of interactions between variables is therefore especially important. This work aimed to analyze the effects of interactions between variables through response surface method (RSM) for uni- and multiplex qPCR, and further optimize the parameters by constructing two mathematical models via RSM and back-propagation neural network-genetic algorithm (BPNN-GA) respectively. The statistical analysis showed that Mg2+ was the most important factor for both uni- and multiplex qPCR. Dynamic models of uni- and multiplex qPCR could be constructed using both RSM and BPNN-GA methods. But RSM was better than BPNN-GA on prediction performance in terms of the mean absolute error (MAE), the mean square error (MSE) and the Coefficient of Determination (R2). Ultimately, optimal parameters of uni- and multiplex qPCR were determined by RSM.

Fabrication and characterization of DDAB/PLA-alginate composite microcapsules as single-shot vaccine

The most effective method to reduce chronic hepatitis B virus infection is the universal implementation of vaccination. The commercial aluminum-based vaccines need multiple-injection protocols for complete protection resulting in poor compliance in developing countries. It is necessary to develop single-shot vaccine formulations. In this study, novel antigen-loaded DDAB/PLA (didodecyldimethylammonium bromide/poly(lactic acid)) nanoparticles (NPs)-alginate composite microcapsules were developed as a single-shot vaccine. The hepatitis B surface antigen (HBsAg)-loaded DDAB/PLA NPs were successfully encapsulated into alginate microcapsules by a modified spray-solidification technique. The response surface method was applied to optimize the preparation parameters employing encapsulation efficiency of HBsAg and particle size of microcapsules as response variables. The antigen-loaded DDAB/PLA NPs-alginate composite microcapsules were prepared under these optimal conditions: the size of composite microcapsules was 24.25 μm, the Span value was 1.627, and the encapsulation efficiency of HBsAg was 68.4%. The obtained microcapsules were spherical gel microparticles with excellent dispersity and narrow size distributions. In vitro release profile indicated a slow release rate of encapsulated HBsAg especially in phosphate buffered saline solution. The microcapsules showed little toxicity in vivo. This vaccine delivery system could induce stronger immune responses by a single shot, which exhibited much higher cytokine secretion levels closely related to cellular immunity and comparable IgG titers to the traditional aluminum-adjuvanted vaccine with three shots.

Formulation of a minimal nutritional medium for enhanced lipid productivity in Chlorella sp. and Botryococcus sp. using response surface methodology

Chlorella sp. MCC 7 and Botryococcus sp. MCC 31 were investigated to enable large-scale biodiesel production from minimal constituents in the growth medium. Response surface methodology (RSM) was used to maximise the biomass productivity and lipid yield using only nitrogen (N), phosphorus (P) and potassium (K) as urea, single super phosphate and muriate of potash. The optimum values were 0.42 g/L nitrogen; 0.14 g/L phosphorus and 0.22 g/L potassium for Chlorella sp.; and 0.46 g/L; 0.14 g/L and 0.25 g/L for Botryococcus sp. Lipid yield of 42% for Chlorella sp. and 52% in Botryococcus sp. was observed. An enhancement in lipid yield by approximately 55% for Chlorella sp. and 73% for Botryococcus sp. was registered as compared to original nutrient medium. Fourier transform infrared (FTIR) analysis of extracted lipids revealed characteristic bands for triglycerides. This study provided utilisation of a practicable nutrient recipe in the form of N, P, K input for enhanced lipid yield from the selected microalgal strains.

Production of lipid-containing microalgal biomass and simultaneous removal of nitrate and phosphate from synthetic wastewater

The major concerns of the modern society such as increasing population, climate change and economic development are imposing continuous stress on water and energy resources. The present work deals with the cultivation of green algae Desmodesmus abundans for optimum biomass productivity and lipid content as well as simultaneous removal of nitrate and phosphate from synthetic wastewater. The algal biomass is characterized by ultimate analysis, scanning electron microscopic analysis and thermogravimetric analysis. The effect of time, inoculum concentration and nitrate concentration on four responses (biomass productivity, lipid content, removal of nitrate and removal of phosphate) are studied by response surface methodology using central composite design. The quadratic models are found to be suitable for each response. At optimized experimental conditions, the algae showed biomass productivity of 46.96 mg L^-1 day^-1, lipid content of 16.23%, nitrate removal of 86.64% and phosphate removal of 87.52% after 27 days, when the initial inoculum concentration was 6% and nitrate concentration was 1.25 g L^-1.

Optimization of Culture Medium Enhances Viable Biomass Production and Biocontrol Efficacy of the Antagonistic Yeast, Candida diversa

Viable biomass production is a key determinant of suitability of antagonistic yeasts as potential biocontrol agents. This study investigated the effects of three metal ions (magnesium, ferrous, and zinc) on biomass production and viability of the antagonistic yeast, Candida diversa. Using response surface methodology to optimize medium components, a maximum biomass was obtained, when the collective Mg²⁺, Fe²⁺, and Zn²⁺ concentrations were adjusted in a minimal mineral (MM) medium. Compared with the unmodified MM, and three ion-deficient MM media, yeast cells cultured in the three ion-modified MM medium exhibited a lower level of cellular oxidative damage, and a higher level of antioxidant enzyme activity. A biocontrol assay indicated that C. diversa grown in the ion-modified MM exhibited the greatest level of control of gray mold on apple fruit. These results provide new information on culture medium optimization to grow yeast antagonists in order to improve biomass production and biocontrol efficacy.

Optimization of critical medium components for enhancing antibacterial thiopeptide nocathiacin I production with significantly improved quality

Nocathiacin I, a glycosylated thiopeptide antibiotic, displays excellent antibacterial activities against multidrug resistant bacterial pathogens. Previously, a novel nocathiacin I formulation for intravenous administration has been successfully developed and its aqueous solubility is greatly enhanced for clinical application. The purpose of the present study was to increase the fermentation titer of nocathiacin I and reduce or eliminate analogous impurities by screening the medium ingredients using response surface methodology. After a sysmatic optimization, a water-soluble medium containing quality-controllable components was developed and validated, resulting in an increase in the production of nocathiacin I from 150 to 405.8 mg·L^-1 at 150-L scale. Meanwhile, the analogous impurities existed in reported processes were greatly reduced or eliminated. Using optimized medium for fermentation, nocathiacin I with pharmaceutically acceptable quality was easily obtained with a recovery of 67%. In conclusion, the results from the present study offer a practical and efficient fermentation process for the production of nocathiacin I as a therapeutic agent.

Strategies for Lipid Production Improvement in Microalgae as a Biodiesel Feedstock

In response to the energy crisis, global warming, and climate changes, microalgae have received a great deal of attention as a biofuel feedstock. Due to a high lipid content in microalgal cells, microalgae present as a promising alternative source for the production of biodiesel. Environmental and culturing condition variations can alter lipid production as well as chemical compositions of microalgae. Therefore, application of the strategies to activate lipid accumulation opens the door for lipid overproduction in microalgae. Until now, many original studies regarding the approaches for enhanced microalgal lipid production have been reported in an effort to push forward the production of microalgal biodiesel. However, the current literature demonstrates fragmented information available regarding the strategies for lipid production improvement. From the systematic point of view, the review highlights the main approaches for microalgal lipid accumulation induction to expedite the application of microalgal biodiesel as an alternative to fossil diesel for sustainable environment. Of the several strategies discussed, the one that is most commonly applied is the design of nutrient (e.g., nitrogen, phosphorus, and sulfur) starvation or limitation. Other viable approaches such as light intensity, temperature, carbon dioxide, salinity stress, and metal influence can also achieve enhanced microalgal lipid production.

Viral infection of the marine alga Emiliania huxleyi triggers lipidome remodeling and induces the production of highly saturated triacylglycerol

Viruses that infect marine photosynthetic microorganisms are major ecological and evolutionary drivers of microbial food webs, estimated to turn over more than a quarter of the total photosynthetically fixed carbon. Viral infection of the bloom-forming microalga Emiliania huxleyi induces the rapid remodeling of host primary metabolism, targeted towards fatty acid metabolism. We applied a liquid chromatography-mass spectrometry (LC-MS)-based lipidomics approach combined with imaging flow cytometry and gene expression profiling to explore the impact of viral-induced metabolic reprogramming on lipid composition. Lytic viral infection led to remodeling of the cellular lipidome, by predominantly inducing the biosynthesis of highly saturated triacylglycerols (TAGs), coupled with a significant accumulation of neutral lipids within lipid droplets. Furthermore, TAGs were found to be a major component (77%) of the lipidome of isolated virions. Interestingly, viral-induced TAGs were significantly more saturated than TAGs produced under nitrogen starvation. This study highlights TAGs as major products of the viral-induced metabolic reprogramming during the host-virus interaction and indicates a selective mode of membrane recruitment during viral assembly, possibly by budding of the virus from specialized subcellular compartments. These findings provide novel insights into the role of viruses infecting microalgae in regulating metabolism and energy transfer in the marine environment and suggest their possible biotechnological application in biofuel production.

Heterotrophic cultivation of Nannochloropsis salina for enhancing biomass and lipid production

Response surface methodology (RSM) was used to enhance the biomass and lipid content in Nannochloropsis salina due to its economic importance. Preliminary screening results revealed that the heterotrophically cultivated N. salina with various carbon and nitrogen sources yielded higher biomass (0.91 ± 0.0035 g/L) and lipid content (37.1 ± 0.49 mg/L) than that of the photoautotrophical cultivation (0.21 ± 0.009 g/L and 22.16 ± 0.27 mg/L). Significant sources that greatly influenced on biomass and lipid content of the alga were optimized through RSM. The medium consisting of glucose (7.959 g/L), sodium acetate (1.46 g/L), peptone (7.6 g/L) and sodium thiosulphate (1.05 g/L) was found to be the optimal concentration for heterotrophic cultivation by response optimizer. Confirmation experiment results for the RSM optimized concentration yielded the biomass of 1.85 g/L and total lipid content of 48.6 mg/L. In this study, we provide with a strategy for enhancing the biomass and lipid content in N. salina.

Efficient lipid extraction and quantification of fatty acids from algal biomass using accelerated solvent extraction (ASE)

Accelerated solvent extraction optimized for extraction of algal lipids and recovery of polyunsaturated fatty acids.

Building a better mousetrap II: using Design of Experiments with unconfounded ions to compare the growth of different microalgae

A large number of unconfounded media variations were used with a Scheffe Mix Model to examine in an unambiguous fashion the effects of variations in six important ions; NH4(+), NO3(-), Na(+), K(+), PO4(-), and Cl(-), on the growth of Chlorella vulgaris. This allows several novel observations on media components, for example, the inhibitory effects of chloride, to be made. Using a side by side comparison, it is shown that two strains of Chlorella show significant physiological and functional differences brought out by this approach. Testing selected formulations with a diverse set of algae demonstrated different effects on both growth and cellular lipid content, in some cases driving significant lipid production. This suggests that future work using a larger portion of media composition space could lead to the development of novel media supporting maximal biomass production and lipid production.

Enzymatic production of biodiesel from Nannochloropsis gaditana lipids: Influence of operational variables and polar lipid content

Fatty acid methyl esters (FAMEs, biodiesel) were produced from Nannochloropsis gaditana wet biomass (12% saponifiable lipids, SLs) by extraction of SLs and lipase catalyzed transesterification. Lipids were extracted by ethanol (96%)-hexane, and 31% pure SLs were obtained with 85% yield. When the lipids were degummed, SL purity increased to 95%. Novozym 435 was selected from four lipases tested. Both the lipidic composition and the use of t-butanol instead of hexane increased the reaction velocity and the conversion, since both decreased due to the adsorption of polar lipids on the lipase immobilization support. The best FAME yield (94.7%) was attained at a reaction time of 48h and using 10mL of t-butanol/g SL, 0.225gN435/g SL, 11:1 methanol/SL molar ratio and adding the methanol in three steps. In these conditions the FAME conversion decreased by 9.8% after three reaction cycles catalyzed by the same lipase batch.