Lipid production and mixotrophic growth features of cyanobacterial strains isolated from various aquatic sites

Improving the biodiesel production in the marine diatom Thalassiosira pseudonana cultivated in nutrient deficiency and sewage water

The use of microalgae as a feedstock in biofuel production is highly encouraging. The marine diatom in this study, Thalassiosira pseudonana, was used as a test organism to evaluate the impact of nitrogen or phosphorus limitation and sewage water on improving biodiesel production. The growth rate is more affected in cultures without phosphorus by 41.8% lower than in control and the highest dry weight estimated in control. The cellular dry weight significantly increased in cultures treated with mix1 and mix2 wastewater compared to the control cultures. Chlorophyll a content decreased in the absence of nitrogen and phosphorous and in sewage water cultures. Lipid content in algal cultures without nitrogen or phosphorus and in sewage water accumulated nearly twice as much lipid content in synthetic medium. T. pseudonana showed high FAME contents; the two most abundant fatty acids, stearic acid (C18:0) and palmitoleic acid (C16:1), in the algal extracts revealed that T. pseudonana was predominantly composed of these fatty acids. T. pseudonana grown in nitrogen or phosphorus-deficient conditions exhibited an extreme percentage of saturated fatty acids (SFAs) by 87.38% and 85.47%, respectively, of the total fatty acids (TFAs). More importantly, the low polyunsaturated fatty acid content in oils indicates a high cetane number, low iodine value, and low corrosion for biodiesel quality indicators. Producing biodiesel that closely meets worldwide biodiesel requirements (ASTM D6751 and EN 14214) is the goal of this work, which shows that growing T. pseudonana under nutrient limitations leads to algal metabolism in that direction.

Impact of macronutrients and salinity stress on biomass and biochemical constituents in Monoraphidium braunii to enhance biodiesel production

Microalgal lipids are precursors to the production of biodiesel, as well as a source of valuable dietary components in the biotechnological industries. So, this study aimed to assess the effects of nutritional (nitrogen, and phosphorus) starvations and salinity stress (NaCl) on the biomass, lipid content, fatty acids profile, and predicted biodiesel properties of green microalga Monoraphidium braunii. The results showed that biomass, biomass productivity, and photosynthetic pigment contents (Chl. a, b, and carotenoids) of M. braunii were markedly decreased by nitrogen and phosphorus depletion and recorded the maximum values in cultures treated with full of N and P concentrations (control, 100%). These parameters were considerably increased at the low salinity level (up to 150 mM NaCl), while an increasing salinity level (up to 250 mM NaCl) reduces the biomass, its productivity, and pigment contents. Nutritional limitations and salt stress (NaCl) resulted in significantly enhanced accumulation of lipid and productivity of M. braunii, which represented more than twofold of the control. Furthermore, these conditions have enhanced the profile of fatty acid and biodiesel quality-related parameters. The current study exposed strategies to improve M. braunii lipid productivity for biodiesel production on a small scale in vitro in terms of fuel quality under low nutrients and salinity stress.

The role of organic nutrients in structuring freshwater phytoplankton communities in a rapidly changing world

Carbon, nitrogen, and phosphorus are critical macroelements in freshwater systems. Historically, researchers and managers have focused on inorganic forms, based on the premise that the organic pool was not available for direct uptake by phytoplankton. We now know that phytoplankton can tap the organic nutrient pool through a number of mechanisms including direct uptake, enzymatic hydrolysis, mixotrophy, and through symbiotic relationships with microbial communities. In this review, we explore these mechanisms considering current and projected future anthropogenically-driven changes to freshwater systems. In particular, we focus on how naturally- and anthropogenically- derived organic nutrients can influence phytoplankton community structure. We also synthesize knowledge gaps regarding phytoplankton physiology and the potential challenges of nutrient management in an organically dynamic and anthropogenically modified world. Our review provides a basis for exploring these topics and suggests several avenues for future work on the relation between organic nutrients and eutrophication and their ecological implications in freshwater systems.

Comparison of Growth Performance, Pigment Synthesis, and Esterase Activity of Synechococcus sp. HS01 and Limnothrix sp. KO01 in Response to Cadmium Toxicity

Various studies have been conducted to understand the impact of environmental pollutants on cyanobacteria due to their abundant presence in aquatic and terrestrial environments, specific morphological and physiological characteristics, and high ecological flexibility in response to environmental changes. Here, the effect of different concentrations of cadmium on two native strains of cyanobacteria, namely Synechococcus sp. HS01 and Limnothrix sp. KO01 was studied and compared with each other. In this regard, the cyanobacterial growth, pigment contents, and esterase enzyme activity were evaluated after exposure of the cells to different concentrations of cadmium (II). The toxic effects of Cd(II) on the growth rate of Limnothrix sp. KO01, even at low concentrations, tended to be higher than those for Synechococcus sp. HS01. The content of pigments decreased by an increase in Cd(II) concentration. In compliance with the cell growth, the changes occurred in pigment contents of Limnothrix sp. KO01 was more sensitive than Synechococcus sp. HS01 in the presence of different concentrations of cadmium. Flow cytometry analysis of Cd(II) effects on esterase activity of both strains after 6, 24, 48, and 72 h of exposure to Cd(II) concentrations of 9, 27, 63, and 90 μM showed that tolerance to Cd(II) toxicity in Limnothrix sp. KO01 is less than Synechococcus sp. HS01. The results obtained in this study suggest high potentials of Synechococcus sp. HS01 for heavy metal bioaccumulation due to its considerable tolerance to cadmium.

Influence of Nutrient Manipulation on Growth and Biochemical Constituent in Anabaena variabilis and Nostoc muscorum to Enhance Biodiesel Production

The present study aims to improve biomass and biochemical constituents, especially lipid production of Anabaena variabilis and Nostoc muscorum by formulating an optimal growth condition using various concentrations of nutrients (NO3−, PO43− and CO32−) for biodiesel production. The supplementation of the three nutrients by +50% showed the maximum dry weight and biomass productivity, while the macromolecule contents were varied. The depletion of N-NO3− by 50% N-NO3− showed the maximum lipid yield (146.67 mg L−1) in A. variabilis and the maximum carbohydrate contents (285.33 mg L−1) in N. muscorum with an increase of 35% and 30% over control of the synthetic medium, respectively. However, variation in P-PO43− and C-CO32− showed insignificant improving results for all biochemical compositions in both cyanobacteria. A. variabilis was the superior species for lipid and protein accumulation; however, N. muscorum showed the maximum carbohydrate content. Accordingly, A. variabilis was selected for biodiesel production. In A. variabilis, −50% N-NO3− resulted in 35% higher lipid productivity compared to the control. Furthermore, the fatty acid profile and biodiesel quality-related parameters have improved under this condition. This study has revealed the strategies to improve A. variabilis lipid productivity for biodiesel production for small-scale in vitro application in terms of fuel quality under low nitrate levels.

Growth Optimization of Lactobacillus acidophilus for Production of Antimicrobial Peptide Acidocin 4356: Scale up from Flask to Lab-Scale Fermenter

Background:

Antibiotic-resistant bacteria are a major threat to global health. Older antibiotics have become more or less ineffective as a result of widespread microbial resistance and an urgent need has emerged for the development of new antimicrobial strategies. Acidocin 4356 is a novel antimicrobial bacteriocin peptide produced by Lactobacillus acidophilus ATCC 4356 and capable of confronting the Pseudomonas aeruginosa ATCC 27853 infection challenges. According to our previous studies, the production of Acidocin 4356 is in parallel with cellular biomass production.

Objectives:

Given the costly production of Acidocin 4356, the development of a beneficial approach for increasing productivity of the cellular biomass has been targeted in the lab-scale fermenter for scale-up production of this bacteriocin. Therefore, in this study, we developed an inexpensive optimal culture medium based on the whey feedstock, evaluating this medium for scaling-up of the bacteriocin production from flask to fermenter.

Material and Methods:

In the first step, the optimization of the process parameters and medium components was carried out using the Plackett-Burman (PB) design and Response surface methodology (RSM) in flask culture. After optimization of the medium, bacteriocin production in the optimum culture medium was compared with de Man, Rogosa and Sharpe (MRS) medium by analyzing the intensity of the peptide band. Intensity analysis has been conducted on the PAGE band of the peptide using Image J software. Finally, the scale- up of bacteriocin production in the optimum culture medium was evaluated by batch fermentation in a 3-liter fermenter.

Results:

In this study, a medium containing whey (40 g.L^-1) and sodium acetate (5 g.L^-1) was used as basal medium, and the effect of other factors were then evaluated. According to the PB design, three factors of peptone concentration, yeast extract concentrations and cultivation temperature were selected as the most effective factors which improve the growth of L. acidophilus. The condition providing the highest growth capacity for bacteriocin production were predicted based on the results of RSM as following: temperature 40 ° C, yeast (4 g.L^-1), and peptone (8 g.L^-1). Finally, the dry cell weight was obtained after incubation for 12 h as 2.25 g.L^-1. Comparison of cell growth and bacteriocin production between MRS medium and optimized medium confirmed the efficacy of these optimal conditions for the cost-effective production of Acidocin 4356 in the flask. Besides, the scale- up of bacteriocin production has made under optimal condition in the 3-L fermenter.

Conclusions:

In this study, for the first time, scale- up production of Acidocin 4356 was presented by using a low-cost method based on whey feedstock to tackle P. aeruginosa infections.

Lipid Production Capacity of a Newly Characterized Cyanobacterial Strain Synechocystissp. MH01: A Comparative Performance Evaluation of Cyanobacterial Lipid-Based Biodiesel

Background:

Cyanobacteria have been the focus of extensive researches because of their high potential for the development of new generations of useful natural compounds with vast applications. For the entire last ten years, a lot of attention has been dedicated to the cyanobacterial lipids as a main source of valuable materials for clean energy production.

Objectives:

As there is a direct relationship between biofuel properties and compositional characteristics of fatty acids, a selected lipid-producing cyanobacterial strain was examined and analyzed in terms of fatty acid composition. The biodiesel quality parameters were carefully examined as well.

Materials and Methods:

A cyanobacterial strain was isolated from waterfalls in the northern part of Iran and identified as Synechocystis sp. MH01. The fatty acids profile of the selected strain, as tested in various culture conditions, was analyzed by gas chromatography (GC) and compared with control subjects to further validating the biodiesel quality parameters.

Results:

The autotrophic cultivation of Synechocystissp. MH01 resulted in biomass and lipid productivity of 109 mg.L^-1 day^-1 and 22.89 mg.L^-1 day^-1, respectively. The mixotrophic cultivation of MH01 strain in sucrose-containing medium led to an approximately 1.8 and 1.22 fold increase in biomass and lipid productivity compared with the autotrophic condition. The addition of glycine to BG11 medium caused up to ~1.3 and ~1.18 fold increase in biomass and lipid productivity compared with control subjects. The analysis of qualitative parameters of the biodiesel, as derived from the lipids, indicated that Synechocystis sp. MH01 has a high ability for lipid production under optimal culture conditions

Conclusions:

It seems feasible to evolve the Synechocystissp. MH01 further particularly for more lipid production as a promising primary raw material for biofuel production through fine-tuning of medium composition

Prospects for the creation of a waste-free technology for wastewater treatment and utilization of carbon dioxide based on cyanobacteria for biodiesel production

Current fresh water and energy shortage determines the need to study the possibilities of using living objects in bioenergy and environmental purification technologies. The development of waste-free technologies allows waste recycling, which saves raw materials and energy, in turn, reducing waste generation. The effect of different carbon dioxide concentrations and wastewater from households on the growth of cyanobacteria was studied in order to determine their capabilities in the purification processes. It was found that the optimal CO₂ concentration for the cultivation of cyanobacteria Cyanobacterium sp. IPPAS B-1200 and Desertifilum sp. IPPAS B-1220 was 10 %, and for the Cyanobacterium aponinum IPPAS B-1201 - 5%. It was revealed that the cultivation of the cyanobacterium Cyanobacterium sp. IPPASB-1200 on wastewater from the water storage reduces the concentration of organic pollutants and, accordingly, improves the physicochemical properties of water. The cleaning percentage for selected pollutants was 68-100 %. It was shown that the most optimal ratio of wastewater to nutrient media for cyanobacteria cultivation were 25:75 and 50:50. The lipid content (%/dry weight) in the biomass of the studied strains of cyanobacteria ranges from 15 to 22% after cultivation in wastewater. It was determined that the strains of Cyanobacterium genus were the most suitable for the production of biodiesel according to their fatty acids composition. It was determined that lipids were composed of only saturated and monounsaturated fatty acids. As a result of the studies, the optimal conditions for the growth of Cyanobacterium sp. IPPAS B-1200 were determined. This microorganism has a good potential to produce biodiesel as a producer of saturated and monounsaturated middle-chain-length fatty acids.

Biological fixation of carbon dioxide and biodiesel production using microalgae isolated from sewage waste water

The present research investigates potential of microalgae isolated from sewage treatment plant to utilize sodium bicarbonate as carbon source for CO₂ sequestration and biodiesel production. Eight algal isolates were isolated from waste water of sewage treatment plant, Amity University Haryana, India. The most potent algal isolates were identified and characterized on the basis of growth and lipid content. The efficient isolates ASW1 and ASW2 were identified as Chlorella sp. and Arthronema sp. by 18srRNA and 16srRNA sequencing method. In both isolates, maximum growth was observed under 20-W fluorescent bulb (3500 flux light intensity) with continuous light cycle of 24 h at pH 9.0 and 25 °C on the 20th day of incubation period. CO₂ utilization efficiency of both algal isolates were observed in terms of total CO₂ consumption rate. Under optimized culture conditions, total lipid content and lipid yield was higher in Arthronema sp. (180 mg l^-1; 32.14%) as compared to Chlorella sp. (98 mg l^-1; 29.6%) in 50 mM NaHCO₃. Transesterified lipids were analysed by GC-MS. The fatty acid methyl ester profile of Arthronema sp. was 34.42% saturated and 65.58% unsaturated fatty acid. Chlorella sp. produces 29.80% saturated and 70.20% unsaturated fatty acid. In both isolates, C16 and C18 fatty acids dominated, which is a promising component for biodiesel. Graphical abstract.

Multifunctional Acidocin 4356 Combats Pseudomonas aeruginosa through Membrane Perturbation and Virulence Attenuation: Experimental Results Confirm Molecular Dynamics Simulation

A longstanding awareness in generating resistance to common antimicrobial therapies by Gram-negative bacteria has made them a major threat to global health. The application of antimicrobial peptides as a therapeutic agent would be a great opportunity to combat bacterial diseases. Here, we introduce a new antimicrobial peptide (∼8.3 kDa) from probiotic strain Lactobacillus acidophilus ATCC 4356, designated acidocin 4356 (ACD). This multifunctional peptide exerts its anti-infective ability against Pseudomonas aeruginosa through an inhibitory action on virulence factors, bacterial killing, and biofilm degradation. Reliable performance over tough physiological conditions and low hemolytic activity confirmed a new hope for the therapeutic setting. Antibacterial kinetic studies using flow cytometry technique showed that the ACD activity is related to the change in permeability of the membrane. The results obtained from molecular dynamic (MD) simulation were perfectly suited to the experimental data of ACD behavior. The structure-function relationship of this natural compound, along with the results of transmission electron microscopy analysis and MD simulation, confirmed the ability of the ACD aimed at enhancing bacterial membrane perturbation. The peptide was effective in the treatment of P. aeruginosa infection in mouse model. The results support the therapeutic potential of ACD for the treatment of Pseudomonas infections.IMPORTANCE Multidrug-resistant bacteria are a major threat to global health, and the Pseudomonas bacterium with the ability to form biofilms is considered one of the main causative agents of nosocomial infections. Traditional antibiotics have failed because of increased resistance. Thus, finding new biocompatible antibacterial drugs is essential. Antimicrobial peptides are produced by various organisms as a natural defense mechanism against pathogens, inspiring the possible design of the next generation of antibiotics. In this study, a new antimicrobial peptide was isolated from Lactobacillus acidophilus ATCC 4356, counteracting both biofilm and planktonic cells of Pseudomonas aeruginosa A detailed investigation was then conducted concerning the functional mechanism of this peptide by using fluorescence techniques, electron microscopy, and in silico methods. The antibacterial and antibiofilm properties of this peptide may be important in the treatment of Pseudomonas infections.

Synechocystis sp. PCC 6803 overexpressing genes involved in CBB cycle and free fatty acid cycling enhances the significant levels of intracellular lipids and secreted free fatty acids

The integrative aspect on carbon fixation and lipid production is firstly implemented in cyanobacterium Synechocystis sp. PCC 6803 using metabolic engineering approach. Genes related to Calvin–Benson–Bassham (CBB) cycle including rbcLXS and glpD and free fatty acid recycling including aas encoding acyl-ACP synthetase were practically manipulated in single, double and triple overexpressions via single homologous recombination. The significantly increased growth rate and intracellular pigment contents were evident in glpD-overexpressing (OG) strain among all strains studied under normal growth condition. The triple aas_glpD_rbcLXS-overexpressing (OAGR) strain notably gave the highest contents of both intracellular lipids and extracellular free fatty acids (FFAs) of about 35.9 and 9.6% w/DCW, respectively, when compared to other strains at day 5 of cultivation. However, the highest intracellular lipid titer and production rate were observed in OA strain at day 5 (228.7 mg/L and 45.7 mg/L/day, respectively) and OG strain at day 10 (358.3 mg/L and 35.8 mg/L/day, respectively) due to their higher growth. For fatty acid (FA) compositions, the main saturated fatty acid of palmitic acid (C16:0) was dominantly found in both intracellular lipid and secreted FFAs fractions. Notably, intracellular FA proportion of myristic acid (C14:0) was induced in all engineered strains whereas the increase of stearic acid (C18:0) composition was found in extracellular FFAs fraction. Altogether, these overexpressing strains efficiently produced higher lipid production via homeostasis balance on both its lipid synthesis and FFAs secretion.

Leptolyngbya fragilis ISC 108 is the most effective strain for dodecane biodegradation in contaminated soils

One of the major environmental problems nowadays is petroleum hydrocarbons contamination. Bioremediation is widely used for cleaning ecosystems contaminated with petroleum hydrocarbons. This study was carried out to investigate the response of five microalgae strains isolated from different regions in Iran for 1% n-dodecane (DOD) degradation. The results revealed that Leptolyngbya fragilis ISC 108 is the most effective strain to utilize n-DOD as growth substrate under a mixotrophic condition. Currently, there is little information about mechanisms involved in microalgae response against DOD. The activity of antioxidant enzymes and total lipid and carbohydrate contents were observed to be greater in DOD-treated L. fragilis ISC 108. Lower values of lipid peroxidation and H₂O₂ along with an increase of dry weight and specific growth rate in L. fragilis ISC 108 under DOD treatment shows that at the cellular level this strain is better equipped with an efficient oxygen radical scavenging system. In conclusion, this study proposes that L. fragilis ISC 108 can be considered an ideal candidate for use in bioremediation of DOD contaminated sites.

Evaluation of Bacterial Lipid Production: Quantitative and Qualitative Measurements: Tips and Guidelines

Over the last decade, finding bacterial strains with ability to accumulate high concentrations of lipids has gained increasing interest, since these lipids may be used in different industries. Here we describe two methods for evaluation of lipid accumulation in cyanobacteria, following by our personal reflection on issues surrounding the use of these methods. First, we present the Bligh and Dyer protocol as a traditional extraction method using organic solvents for quantitative determination of lipids and next Nile red, a selective fluorescent stain, that has been used as a rapid approach for both qualitative and quantitative measurement of lipids.

Significant increase in cyanide degradation by Bacillus sp. M01 PTCC 1908 with response surface methodology optimization

Cyanide is used in many industries despite its toxicity. Cyanide biodegradation is affordable and eco-friendly. Sampling from cyanide-contaminated areas from the Muteh gold mine and isolation of 24 bacteria were performed successfully. The selected bacteria-'Bacillus sp. M01'-showed maximum tolerance (15 mM) to cyanide and deposited in Persian Type Culture Collection by PTCC No.: 1908. In the primary experiments, effective factors were identified through the Plackett-Burman design. In order to attain the maximum degradation by Bacillus sp. M01 PTCC 1908, culture conditions were optimized by using response surface methodology. By optimizing the effective factor values and considering the interaction between them, the culture conditions were optimized. The degradation percentage was calculated using one-way ANOVA vs t test, and was found to have increased 2.35 times compared to pre-optimization. In all of the experiments, R² was as high as 91%. The results of this study are strongly significant for cyanide biodegradation. This method enables the bacteria to degrade 86% of 10 mM cyanide in 48 h. This process has been patented in Iranian Intellectual Property Centre under Licence No: 90533.

Improved biomass and lipid production in Synechocystis sp. NN using industrial wastes and nano-catalyst coupled transesterification for biodiesel production

In this study, the improved biomass (1.6 folds) and lipid (1.3 folds) productivities in Synechocystis sp. NN using agro-industrial wastes supplementation through hybrid response surface methodology-genetic algorithm (RSM-GA) for cost-effective methodologies for biodiesel production was achieved. Besides, efficient harvesting in Synechocystis sp. NN was achieved by electroflocculation (flocculation efficiency 97.8±1.2%) in 10min when compared to other methods. Furthermore, different pretreatment methods were employed for lipid extraction and maximum lipid content of 19.3±0.2% by Synechocystis sp. NN was attained by ultrasonication than microwave and liquid nitrogen assisted pretreatment methods. The highest FAME (fatty acid methyl ester) conversion of 36.5±8.3mg FAME/g biomass was obtained using titanium oxide as heterogeneous nano-catalyst coupled whole-cell transesterification based method. Conclusively, Synechocystis sp. NN may be used as a biodiesel feedstock and its fuel production can be enriched by hybrid RSM-GA and nano-catalyst technologies.

Two-stage (photoautotrophy and heterotrophy) cultivation enables efficient production of bioplastic poly-3-hydroxybutyrate in auto-sedimenting cyanobacterium

Sustainable production of bioplastics by heterotrophic microbes has been restricted by the limited resources of organic substrates and the energy required for biomass harvest. Here, the easy-to-harvest cyanobacterium (Chlorogloea fritschii TISTR 8527), from which the biomass instantaneously settled to the bottom of liquid culture, was utilized to produce poly-3-hydroxybutyrate (PHB) using a two-stage cultivation strategy. The cells were first pre-grown under normal photoautotrophy to increase their biomass and then recultivated under a heterotrophic condition with a single organic substrate to produce the product. Through optimization of this two-stage cultivation, the mass conversion efficiency of acetate substrate to PHB was obtained at 51 ± 7% (w/w), the comparable level to the theoretical biochemical conversion efficiency of acetate to PHB. This two-stage cultivation that efficiently converted the substrate to the product, concurrent with a reduced culture biomass, may be applicable for the production of other biopolymers by cyanobacteria.

Green renewable energy production from Myxosarcina sp.: media optimization and assessment of biodiesel fuel properties

In this study,Myxosarcinasp. was evaluated for biomass and lipid productionviathe supplementation of sugar industrial waste (SIW) and sodium chloride (NaCl), and medium optimization with response surface methodology (RSM) for biodiesel production.

Physiochemical and thermodynamic characterization of lipopeptide biosurfactant secreted by Bacillus tequilensis HK01

An extensive investigation was applied to isolate biosurfactant producing bacteria from urban waste.