Mixotrophic Research Articles

Stoichiometry of carbon, nitrogen and phosphorus is closely linked to trophic modes in orchids

BackgroundMycorrhiza is a ubiquitous form of symbiosis based on the mutual, beneficial exchange of resources between roots of autotrophic (AT) plants and heterotrophic soil fungi throughout a complex network of fungal mycelium. Mycoheterotrophic (MH) and mixotrophic (MX) plants can parasitise this system, gaining all or some (respectively) required nutrients without known reciprocity to the fungus. We applied, for the first time, an ecological stoichiometry framework to test whether trophic mode of plants influences their elemental carbon (C), nitrogen (N), and phosphorus (P) composition and may provide clues about their biology and evolution within the framework of mycorrhizal network functioning.ResultsWe analysed C:N:P stoichiometry of 24 temperate orchid species and P concentration of 135 species from 45 plant families sampled throughout temperate and intertropical zones representing the three trophic modes (AT, MX and MH). Welch’s one-way ANOVA and PERMANOVA were used to compare mean nutrient values and their proportions among trophic modes, phylogeny, and climate zones. Nutrient concentration and stoichiometry significantly differentiate trophic modes in orchids. Mean foliar C:N:P stoichiometry showed a gradual increase of N and P concentration and a decrease of C: nutrients ratio along the trophic gradient AT < MX < MH, with surprisingly high P requirements of MH orchids. Although P concentration in orchids showed the trophy-dependent pattern regardless of climatic zone, P concentration was not a universal indicator of trophic modes, as shown by ericaceous MH and MX plants.ConclusionThe results imply that there are different evolutionary pathways of adaptation to mycoheterotrophic nutrient acquisition, and that the high nutrient requirements of MH orchids compared to MH plants from other families may represent a higher cost to the fungal partner and consequently lead to the high fungal specificity observed in MH orchids.

Coupling wastewater valorization with sustainable biofuel production: Comparison of lab- and pilot-scale biomass yields of Chlorella sorokiniana grown in wastewater under photoautotrophic and mixotrophic conditions.

Microalgae are the important biofuel precursors and their economic cultivation can be boosted under mixotrophic (MT) conditions while employing different industrial wastewaters containing organic carbon. In the current research, the quantitative analysis of microalgal biomass production under MT and photoautotrophic (PT) cultivation conditions both at lab and pilot scales was studied. For the purpose, a pre-identified microalgal species Chlorella sorokiniana was cultivated mixotrophically and photoautotrophically at lab and pilot scales. Artificially prepared wastewater containing 2% (w/v) sugarcane molasses was used for MT cultivation. However, for PT cultivation, atmospheric CO2 was the only carbon source. After 15 days of aerobic incubation, microalgal biomass was harvested and analyzed for biomass productivity. Cultivation conditions and cultivation scale posed significant and non-significant impact, respectively on biomass productivities. However, biomass productivity was comparatively higher for the biomass raised under MT conditions at lab scale. The recorded values of biomass productivity were 88.75±9.51 and 127.68±7.91mgL-1d-1 for the biomass raised at lab scale under PT and MT conditions, respectively. Pilot-scale cultivation depicted biomass productivities as 83.49±7.87 and 124.88±3.76mgL-1d-1 under PT and MT conditions, respectively. High biomass production under MT conditions may suggest the elevated production of biofuels from microalgae. Future studies on biomass production while utilizing different industrial wastewaters at pilot scale and in open raceway ponds are needed for viable production of microalgae-based fuels.

A new pilot-scale fermentation mode enhances Euglena gracilis biomass and paramylon (β-1,3-glucan) production

Paramylon (β-1,3-glucan) extracted from the microalga Euglena gracilis has a range of applications. However, the industrial production of E. gracilis biomass and paramylon is limited by bench-scale conditions. This study utilized a new pilot-scale fermentation mode by combining mixotrophic (MT) and heterotrophic (HT) conditions to evaluate the changes in E. gracilis biomass and paramylon production. This new mode revealed that cell viability was enhanced under MT conditions and paramylon had accumulated under HT conditions. Maximal biomass and paramylon contents were 86.2 g/L and 78.2%, respectively. Metabolomics analysis revealed that the citrate cycle, related amino acids, and the glycerophospholipid biosynthetic pathway were upregulated under MT conditions, while the carbon skeleton entered the paramylon synthesis pathway under HT conditions. These findings present a valuable theoretical basis for the industrial production of E. gracilis and other microalgae.

Five &lt;italic&gt;Alexandrium&lt;/italic&gt; species lacking mixotrophic ability

Five &lt;italic&gt;Alexandrium&lt;/italic&gt; species lacking mixotrophic ability

Morphological characterization, growth appraisal, and probing biofuels potential of newly isolated Scenedesmus sp. from desert Cholistan.

Microalgae have an excellent potential for producing valuable natural products, including biofuels. Therefore, it is imperative to explore and document the existing microalgal flora and utilize their potentials to cope the increasing human needs. The present work aims at exploring and characterizing newly isolated microalgae from desert Cholistan, a habitat with myriad algal diversity. Light microscopy, scanning electron microscopy, and molecular phylogenetic approaches were used for species-level identification. Characterization and growth optimization of Scendesmus sp. were analyzed under three different growth modes to determine the most favorable conditions for increasing biomass, growth rate, and lipid content. The results revealed that mixotrophic (MT) mode significantly increases photosynthetic activity, growth rate, and lipid content with glycerol as supplement carbon source. The investigated Scenedesmus dimorphous produced a maximum dry weight of 1.73 g L-1 , improved fatty acid methyl esters profile and yield lipid up to 40% of DCW (68 g L-1 ) under MT mode, which is almost double to that of photoautotrophic cultivation. The glycerol availability in medium has been identified as the critical element for boosting growth and lipid content. Thus, it can reduce the cost of biofuel production.

Comparative proteomics investigation of central carbon metabolism in Euglena gracilis grown under predominantly phototrophic, mixotrophic and heterotrophic cultivations

Euglena gracilis can use a wide range of organic carbon sources, as well as CO2 from the atmosphere. This metabolic versatility is owed to the genome of E. gracilis that can encode a wide range of enzymes. Many of these enzymes are regulated post-transcriptionally, allowing the cells to adapt quickly to changes in their surroundings. Here we investigated the effect of predominantly phototrophic (PT), mixotrophic (MT) and heterotrophic (HT) cultivation on central carbon metabolism in E. gracilis Z using label-free shotgun proteomics. Differential expression between isozymes was observed based on the cultivation condition. A hexokinase enzyme identified in the published transcriptome was not detected in the proteome. Instead, a high-specificity glucokinase appeared to conduct the first step of glycolysis. Two candidates for paramylon synthase were identified (EgGSL1 and EgGSL2), of which the predominant EgGSL2 protein was detected across all growth conditions, while EgGSL1 was only detected in the presence of light (PT and MT cultivations). Proteomic analysis revealed that the oxidative pentose phosphate pathway also plays a key role in glucose metabolism under MT and HT cultivation. Some chloroplast-encoded proteins and enzymes of the Calvin pathway were detected under HT cultivation indicating regulation at the post-translational level. The carbon metabolic pathways investigated here in terms of proteomic changes provide new information, as well as validate data presented elsewhere with quantitative proteomics, adding to the existing knowledge of metabolism in E. gracilis. Putative functional annotations of several proteins that were previously unidentified are also provided.

Evaluation of Thiosulfate-Based Autotrophic and Mixotrophic Denitrification Performances under Different Operational Conditions

Bu calismanin amaci ototrofik ve miksotrofik denitrifikasyon proses performanslarini etkileyen faktorlerin ardisik kesikli reaktorde arastirilmasidir. Calisma verileri ototrofik denitrifikasyon prosesinin karbon icerigi dusuk atiksular icin gercek olcekte uygulanabilirligine isik tutmaktadir. Ototrofik denitrifikasyon prosesinde farkli dongu suresi, elektron vericive organik karbon ilavesinin nitrat giderim performansina etkisi sulfat, nitrat, nitrit, ORP ve inorganik karbon parametreleri ile degerlendirilmistir. Calismanin ilk asamasinda farkli dongu surelerinin (8sa-4sa-2sa) tiyosulfat (S 2 O 3 -2 ) bazli ototrofik denitrifikasyon prosesine etkisi arastirilmistir. Daha sonra 2 saatlik optimum dongu suresinde farkli S 2 O 3 -2 /NO 3 - oranlari (1,5-1,25-1) ile ototrofik denitrifikasyon prosesinin optimizasyon calismalari yurutulmustur. Elde edilen calisma bulgulari goz onunde bulunduruldugunda maksimum %84 nitrat giderim verimi 2 saatlik dongu suresi ve 1,5 S 2 O 3 -2 /NO 3 - orani ile isletilen isletim kosullarindan elde edilmistir. Calismanin son asamasinda ise farkli C/N (0,35-0,70-1,05) oranlarinin miksotrofik denitrifikasyon performansina etkisi incelenmistir ve C/N oranin 1,05 oldugu isletim kosulunda nitratin tamami tuketilirken organik madde kaynagi olarak metanolun artmasiyla nitrat giderim hizinin arttigi gozlemlenmistir.

A comprehensive assessment of the biosynthetic pathways of ascorbate, α-tocopherol and free amino acids in Euglena gracilis var. saccharophila

Euglena gracilis produces several important health-enhancing metabolites including ascorbate, α-tocopherol and free amino acids (faa). The yield of metabolites is dependent on the strain of E. gracilis and the metabolic growth condition. Here we investigated the effects of photoautotrophic (PT), mixotrophic (MT) and heterotrophic (HT) cultivation on the synthesis of ascorbate, α-tocopherol and faa in E. gracilis var. saccharophila, using label-free shotgun proteomics, and metabolite analysis using colourimetric assay, high-performance and ultra-performance liquid chromatography (HPLC/UPLC). PT cultivation resulted in the production of more antioxidants (up to 4.13mgg−1 ascorbate and 2.52mgg−1 α-tocopherol) than the MT and HT growth conditions (up to 0.97 and 0.50mgg−1 ascorbate, and 1.40 and 0.21mgg−1 α-tocopherol, respectively). The relative abundance of several faa varied between mid-log and initial stationary growth phases, but the total amount of faa remained about the same, with arginine as the most abundant amino acid. Proteomic analysis revealed a total of 3843 non-redundant proteins in E. gracilis var. saccharophila, of which 1890 were common among all cultivations. Gene ontology annotations suggested derivatisation of metabolic pathways from different organisms, such as lysine biosynthesis from fungi and serine biosynthesis from plants, while a few pathways were unique to Euglena, such as those of ascorbate and arginine. Some enzymes exhibited several isoforms that were influenced by the metabolic growth condition. For example, one of the isozymes of threonine aldolase was expressed in HT/MT cultures only, and one of the isozymes of phosphoglycerate dehydrogenase was expressed in PT cultures only. This is the first proteomic study of E. gracilis var. saccharophila, which provides a mechanistic insight into the biosynthetic pathway dynamics of primary metabolites (antioxidants and faa). This new information can serve as a framework for further development of Euglena as a producer of nutraceuticals.

The preliminary study of lipid production of Nostoc sp. from Bueng Boraphet, Nakhon Sawan Province

Our study was focused on optimum physical and nutritional conditions in lipid accumulation of microalgae (Nostoc sp.) from Bueng Boraphet using BG-11 as cultured media. Results showed that the optimum temperature and acid-base value were at 30 oC and pH 7.0, respectively under autotrophic condition. Nostoc sp. was able to properly grow and gave 0.517 g/L dry cell weight and 4.16% lipid content. The optimum nutrition for lipid accumulation by Nostoc sp. was then examined. These conditions were found to be 0.15% potassium nitrate (KNO3), 10% glucose and 0.004% dipotassium phosphate (K2HPO4) at 30 oC, pH 7.0 under mixotrophic condition. Nostoc sp. showed the highest dry cell weight and lipid content at 1.314 g/L and 4.48 percent respectively. The trend of lipid accumulation was depend on the growth rate of Nostoc sp.

Sustainability Evaluation of Biodiesel from Arthrospira Platensis and Chlorella Vulgaris Under Mixotrophic Conditions and Salinity Stress

Sustainability Evaluation of Biodiesel from Arthrospira Platensis and Chlorella Vulgaris Under Mixotrophic Conditions and Salinity Stress

Sulfate reduction and mixotrophic sulfide-utilization denitrification integrated biofilm process for sulfate-laden wastewater treatment and sulfur recovery.

A novel and integrated biofilm process--the sulfate reduction (SR) and mixotrophic (MR) sulfide-utilization denitrification process (SMSD)--was recently proposed for sulfate treatment and sulfur recovery. The process consisted of two bioreactors: a 5.1 L anaerobic upflow reactor for SR, and a 3.5 L anaerobic upflow reactor for MR desulfurization-denitrification. The experiment was conducted for 370 days to evaluate the performance of SMSD at various sulfate concentrations and hydraulic retention times. The process successfully achieved sulfate, organics and nitrogen compound removal efficiencies of 94.1, 97.7 and 99.1%, respectively. Sulfate was predominantly converted to element sulfur, while nitrate and nitrite were finally converted to nitrogen gas. In SR, with the help of high pH and sponge cubes with various bacteria, 97.5% of sulfide conversion efficiency and 540 mgS/L of sulfide were obtained. In MR, sulfide was removed up to 100% and was partially oxidized to sulfur. The extent of heterotrophic denitrification, which ranged from 35.8 to 59.8%, depended on the categories of electron acceptors.

Cultivation of microalga, Chlorella vulgaris under different auto–hetero–mixo trophic growths as a raw material during biodiesel production and cost evaluation

The biomass and lipid productivities of green microalga, Chlorella vulgaris TISTR 8580 cultivated in the Bold's basal medium under three different culture conditions namely AC (autotrophic), HC (heterotrophic) and MC (mixotrophic) cultivations in a 20 L rectangular bioreactor were investigated. Maximum cell growths were obtained on day 10, 3 and 5 under AC, HC and MC, respectively. The C. vulgaris cells in heterotrophic condition contained the highest amount of lipids (32.9%) and the lowest amount of proteins (14.5%). The composition of C. vulgaris cells under MC condition was found to be between those found at AC and HC conditions. The most efficient energy production system in terms of lipid production to energy consumption was MC. The biodiesel yield was about 93.3% and fatty acid in methyl esters were found as 35.33% palmitic acid, 19.01% oleic acid, 19.21% linoleic acid, 11.68% linolenic acid and 14.77% others.

Suitability of Chlorella vulgaris UAM 101 for heterotrophic biomass production

The dry weight production of mixotrophic (MX), photoheterotrophic (PH) and chemoheterotrophic (QH) batch cultures of Chlorella vulgaris UAM 101 in the presence of glucose is always larger than that of the control cultures grown photoautotrophically (PA). The rates of mitochondrial respiration and of nitrate uptake are strongly stimulated in the three different models of heterotrophic growth. Glucose also promotes a marked increase of photosynthetic O 2 evolution of mixotrophic cultures. There is a reduction in the protein content of mixotrophic cells, which is compensated by an increase in lipids and carbohydrates. The enhancement of the main physiological processes in the presence of glucose accounts for the heterotrophic potential of this strain.

Autotrophic and mixotrophic growth of three thermoacidophilic iron-oxidizing bacteria

Etude physiologique de 3 souches dont l'une n'a pas encore ete decrite, comparaison avec les Thiobacillus