Comparison of the culture and harvesting of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> and <Emphasis Type="Italic">Tetradesmus obliquus</Emphasis> for the removal of pharmaceuticals from water

The objective of this work was to assess and compare the removal efficiency of paracetamol and salicylic acid from aqueous medium by a microalgae-based treatment, using either Chlorella vulgaris or Tetradesmus obliquus. Moreover, considering microalgae application in wastewater treatment, the influence of these pharmaceuticals in the algal nutrient removal capacity was evaluated. The removal of paracetamol by T. obliquus (>40 %) was larger than by C. vulgaris (>21 %) in batch culture, and this was also observed for salicylic acid (>93 % by T. obliquus and >25 % by C. vulgaris). Both strains removed nutrients (phosphate and nitrate) almost completely by the end of the batch culture, but T. obliquus showed the highest efficiency at the steady state conditions of the semicontinuous culture. In spite of this, under the flocculants here tested, the efficiency in the recovery of biomass was much higher for C. vulgaris. These results highlight the importance of strain selection in the application of microalgae for wastewater treatment and, particularly, for the removal of pharmaceuticals.     

Application of <Emphasis Type="Italic">Chlorella sorokiniana</Emphasis> (Chlorophyceae) as supplement and/or an alternative medium for the in vitro cultivation of <Emphasis Type="Italic">Schomburgkia crispa</Emphasis> (Orchidaceae)

Schomburgkia crispa Lindley (Orchidaceae) is an epiphytic species found in gallery forests and dry vegetation in the Brazilian Cerrado. It is typically unable to germinate or exhibits low germination because of dependency on mycorrhizal associations. In vitro cultivation techniques have helped circumvent difficulties involved in propagation from seeds. Alternative media and organic biostimulant substances that reduce costs and promote satisfactory in vitro growth are constantly sought. This study evaluated in vitro multiplication and rooting of S. crispa in a modified culture medium containing extract of the microalga Chlorella sorokiniana. We analyzed supplementation of WPM (Woody Plant Medium) with microalgae suspended in NPK medium, or as the supernatant resulting from the centrifugation of a culture in NPK medium. The extracts were added to WPM instead of distilled water. The compounds 6-benzylaminopurine (BAP) and indolebutyric acid (IBA) were used as reference in the in vitro multiplication and rooting of S. crispa, respectively. Both growth regulators were tested at 0, 2.5, and 5.0 mg L^?1. During in vitro multiplication of S. crispa, WPM supplemented with 5.0 mg L^?1 BAP favored the formation of more sprouts, whereas WPM containing 2.5 mg L^?1 IBA supplemented with microalgae extract stimulated in vitro rooting. Schomburgkia crispa explants cultivated in medium supplemented with microalgae suspension or the supernatant of C. sorokiniana showed growth similar to explants cultivated in WPM alone. Therefore, it is possible to use the microalga C. sorokiniana as a supplement and/or alternative to WPM for the in vitro cultivation of S. crispa.     

Comparison of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> and cyanobacterial biomass: cultivation in urban wastewater and methane production

Anaerobic digestion of microalgae is hampered by its complex cell wall. Against this background, cyanobacteria cell walls render this biomass as an ideal substrate for overcoming this drawback. The aim of the present study was to compare the growth of two cyanobacteria (Aphanizomenon ovalisporum and Anabaena planctonica) and a microalga (Chlorella vulgaris) in urban wastewater when varying the temperature (22, 27 and 32 °C). Cyanobacterial optimal growth for both strains was attained at 22 °C, while C. vulgaris did not show remarkable differences among temperatures. For all the microorganisms, ammonium removal was higher than phosphate. Biomass collected was subjected to anaerobic digestion. Methane yield of C. vulgaris was 184.8 mL CH₄ g COD in^?1 while with A. ovalisporum and A. planctonica the methane production was 1.2- and 1.4-fold higher. This study showed that cyanobacteria growth rates could be comparable to microalgae while presenting the additional benefit of an increased anaerobic digestibility.     

Thermostable phycocyanin from the red microalga <Emphasis Type="Italic">Cyanidioschyzon merolae</Emphasis>, a new natural blue food colorant

The demand for natural food colorants is growing as consumers question the use of artificial colorants more and more. The phycobiliprotein C-phycocyanin of Arthospira platensis is used as a natural blue colorant in certain food products. The thermoacidophilic red microalga Cyanidioschyzon merolae might provide an alternative source of phycocyanin. Cyanidioschyzon merolae belongs to the order Cyanidiophyceae of the phylum Rhodophyta. Its natural habitat are sulfuric hot springs and geysers found near volcanic areas in, e.g., Yellowstone National Park in the USA and in Java, Indonesia. It grows optimally at a pH between 0.5 and 3.0 and at temperatures up to 56 °C. The low pH at which C. merolae grows minimizes the risk of microbial contamination and could limit production loss. As C. merolae lacks a cell wall, phycocyanin with a high purity number of 9.9 could be extracted by an osmotic shock using a simple ultrapure water extraction followed by centrifugation. The denaturation midpoint at pH 5 was 83 °C, being considerably higher than the A. platensis phycocyanin (65 °C). The C. merolae phycocyanin was relatively stable at pH 4 and 5 up to 80 °C. The high thermostability at slightly acidic pH makes the C. merolae phycocyanin an interesting alternative to A. platensis phycocyanin as a natural blue food colorant.     

Effects of <Emphasis Type="Italic">Ascophyllum nodosum</Emphasis> extract on growth and antioxidant defense systems of two freshwater microalgae

Microalgae in genus Chlorella and Scenedesmus are common in aquatic ecosystems and are widely used for various studies on algal growth and applications. Macroalgae may play an important role for control of microalgal growth, attributable to their rich content of bioactive compounds. In this study, the brown seaweed Ascophyllum nodosum was extracted with 70% acetone and the extract was used to treat the green microalgae, Chlorella vulgaris and Scenedesmus sp. Cell density and chlorophyll a concentration were used as growth indexes to evaluate the effects of A. nodosum extract (ANE) on the microalgae. The ANE with concentrations > 1% exhibited significant capability of inhibition of the growth of microalgae by over 80%. On the contrary, 1% ANE caused varying degrees of acceleration of cell proliferation and chlorophyll a synthesis in C. vulgaris and Scenedesmus sp., respectively. Analysis of antioxidant activities of the enzymes superoxide dismutase (SOD) and catalase (CAT) revealed the impact of ANE on the antioxidant defense system of the microalgae. The SOD and CAT activities were significantly depressed by high concentrations (> 2%) ANE, while a slight increase of the enzyme activities was observed with 1% ANE at the early period, which could be correlated to the growth response. Therefore, the mechanism of microalgae control could be related to the interaction between the ANE and the antioxidant defense systems. Phlorotannins are proposed as the principal algistatic components in the ANE which could be utilized in controlling microalgae growth.     

Cultivation of shear stress sensitive and tolerant microalgal species in a tubular photobioreactor equipped with a centrifugal pump

The tolerance to shear stress of Tetraselmis suecica, Isochrysis galbana, Skeletonema costatum, and Chaetoceros muelleri was determined in shear cylinders. The shear tolerance of the microalgae species strongly depends on the strain. I. galbana, S. costatum, and C. muelleri exposed to shear stress between 1.2 and 5.4 Pa resulted in severe cell damage. T. suecica is not sensitive to stresses up to 80 Pa. The possibility to grow these algae in a tubular photobioreactor (PBR) using a centrifugal pump for recirculation of the algae suspension was studied. The shear stresses imposed on the algae in the circulation tubes and at the pressure side of the pump were 0.57 and 1.82 Pa, respectively. The shear stress tolerant T. suecica was successfully cultivated in the PBR. Growth of I. galbana, S. costatum, and C. muelleri in the tubular PBR was not observed, not even at the lowest pumping speed. For the latter shear sensitive strains, the encountered shear stress levels were in the order of magnitude of the determined maximum shear tolerance of the algae. An equation was used to simulate the effect of possible damage of microalgae caused by passages through local high shear zones in centrifugal pumps on the total algae culture in the PBR. This simulation shows that a culture of shear stress sensitive species is bound to collapse after only limited number of passages, confirming the importance of considering shear stress as a process parameter in future design of closed PBRs for microalgal cultivation.     

Potential Outdoor Cultivation of Green Microalgae Based on Response to Changing Temperatures and by Combining with Air Temperature Occurrence

In this study, our working hypothesis was to examine whether temperature alters biomass and metabolite production by microalgae according to strain. We also addressed whether it is possible to choose a strain suitable for growing in each season of a given region. A factorial experiment revealed a significant interaction between chlorophylls a and b (Chl a and Chl b), carotenoid/Chl (a?+?b) ratio, biomass and total lipid productivity of six green microalgae (four Chlorella spp., Chlorella sorokiniana and Neochloris oleoabundans) after 15 days at four temperatures. At 39/35 °C, two Chlorella sp. strains (IPR7115 and IPR7117) showed higher total carotenoids/Chl (a?+?b) (0.578 and 0.830), respectively. N. oleoabundans had the highest Chl a (8210 μg L^?1) and Chl b (1909 μg L^?1) at 19/15 °C and highest maximum dry biomass (2900 mg L^?1), specific growth rate (0.538 day^?1) and total lipids (1003 mg L^?1) at 15/8 °C. We applied a method to infer the growth of these six green microalgae in outdoor ponds, as based on their response to changing temperatures and by combining with historical data on day/night air temperature occurrence for a given region. We conclude that the use of regionalized maps based on air temperature is a good strategy for predicting microalgal cultivation in outdoor ponds based on their features and tolerance to changing temperature.     

The Plant Alkaloid Camptothecin as a Novel Antifouling Compound for Marine Paints: Laboratory Bioassays and Field Trials

The extensive use of copper and booster biocides in antifouling (AF) paints has raised environmental concerns and the need to develop new AF agents. In the present study, 18 alkaloids derived from terrestrial plants were initially evaluated for AF activity using laboratory bioassays with the bryozoan Bugula neritina and the barnacle Balanus albicostatus. The results showed that 4 of the 18 alkaloids were effective in inhibiting larval settlement of B. neritina, with an EC₅₀ range of 6.18 to 43.11 μM, and 15 of the 18 alkaloids inhibited larval settlement of B. albicostatus, with EC₅₀ values ranging from 1.18 to 67.58 μM. Field trials that incorporated five alkaloids respectively into paints with 20% w/w indicated an in situ AF efficiency of evodiamine, strychnine, camptothecin (CPT), and cepharanthine, with the most potent compound being CPT, which also exhibited stronger AF efficiency than the commercial antifoulants cuprous oxide and zinc pyrithione in the field over a period of 12 months. Further field trials with different CPT concentrations (0.1 to 20% w/w) in the paints suggested a concentration-dependent AF performance in the natural environment, and the effective concentrations to significantly inhibit settlement of biofoulers in the field were ≥?0.5% w/w (the efficiency of 0.5% w/w lasted for 2 months). Moreover, CPT toxicity against the crustacean Artemia salina, the planktonic microalgae Phaeodactylum tricornutum and Isochrysis galbana, was examined. The results showed that 24 h LC₅₀ of CPT against A. salina was 20.75 μM, and 96 h EC₅₀ (growth inhibition) values of CPT to P. tricornutum and I. galbana were 55.81 and 6.29 μM, respectively, indicating that CPT was comparatively less toxic than several commercial antifoulants previously reported. Our results suggest the novel potential application of CPT as an antifoulant.     

Magnetophoretic harvesting of freshwater microalgae using polypyrrole/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposite and its reusability

A magnetophoretic harvesting agent, a polypyrrole/Fe₃O₄ magnetic nanocomposite, is proposed as a cost and energy efficient alternative to recover biomass of the microalgae Botryococcus braunii, Chlorella protothecoides, and Chlorella vulgaris from their culture media. The maximal recovery efficiency reached almost 99 % for B. braunii, 92.4 % for C. protothecoides, and 90.8 % for C. vulgaris. The maximum adsorption capacity (Q ₀) of the magnetic nanocomposite for B. braunii (63.49 mg dry biomass mg^?1 PPy/Fe₃O₄) was higher than that for C. protothecoides (43.91 mg dry biomass mg^?1 PPy/Fe₃O₄) and C. vulgaris (39.98 mg dry biomass mg^?1 PPy/Fe₃O₄). The highest harvesting efficiency for all the studied microalgae were at pH 10.0, and measurement of zeta-potential confirmed that the flocculation was induced by charge neutralization. This study showed that polypyrrole/Fe₃O₄ can be a promising flocculant due to its high efficacy, low dose requirements, short settling time, its integrity with cells, and with great potential for saving energy because of its recyclability.     

Microalgae from the Selenastraceae as emerging candidates for biodiesel production: a mini review

Over the years, microalgae have been identified to be a potential source of commercially important products such as pigments, polysaccharides, polyunsaturated fatty acids and in particular, biofuels. Current demands for sustainable fuel sources and bioproducts has led to an extensive search for promising strains of microalgae for large scale cultivation. Prospective strains identified for these purposes were among others, mainly from the genera Hematococcus, Dunaliella, Botryococcus, Chlorella, Scenedesmus and Nannochloropsis. Recently, microalgae from the Selenastraceae emerged as potential candidates for biodiesel production. Strains from the Selenastraceae such as Monoraphidium sp. FXY-10, M. contortum SAG 47.80, Ankistrodesmus sp. SP2-15 and M. minutum were high biomass and lipid producers when cultivated under optimal conditions. A number of Selenastraceae strains were also reported to be suitable for cultivation in wastewater. This review highlights recent reports on potential strains from the Selenastraceae for biodiesel production and contrasts their biomass productivity, lipid productivity as well as fatty acid profile. Cultivation strategies employed to enhance their biomass and lipid productivity as well as to reduce feedstock cost are also discussed in this paper.     

The effect of temperature on growth and lipid and fatty acid composition on marine microalgae used for biodiesel production

Cultivation temperature is one of the major factors affecting the growth and lipid accumulation of microalgae. In this study, the effects of temperature on the growth, lipid content, fatty acid composition and biodiesel properties of the marine microalgae Chaetoceros sp. FIKU035, Tetraselmis suecica FIKU032 and Nannochloropsis sp. FIKU036 were investigated. These species were cultured at different temperatures (25, 30, 35 and 40 °C). The results showed that the specific growth rate, biomass and lipid content of all microalgae decreased with increasing temperature. With regards to fatty acids, the presence of saturated fatty acids (SFAs) in T. suecica FIKU032 and Nannochloropsis sp. FIKU036 decreased with increasing temperature, in contrast with polyunsaturated fatty acids (PUFAs). Moreover, Chaetoceros sp. FIKU035 was the only species that could grow at 40 °C. The highest lipid productivity was observed in Chaetoceros sp. FIKU035 when cultivated at 25 °C (66.73 ± 1.34 mg L^?1 day^?1) and 30 °C (61.35 ± 2.89 mg L^?1 day^?1). Moreover, the biodiesel properties (cetane number, cold filter plugging point, kinematic viscosity and density) of the lipids obtained from this species were in accordance with biodiesel standards. This study indicated that Chaetoceros sp. FIKU035 can be considered as a suitable species for biodiesel production in outdoor cultivation.     

Temperature-induced changes in treatment efficiency and microbial structure of aerobic granules treating landfill leachate

This paper investigates the effect of temperature on nitrogen and carbon removal by aerobic granules from landfill leachate with a high ammonium concentration and low concentration of biodegradable organics. The study was conducted in three stages; firstly the operating temperature of the batch reactor with aerobic granules was maintained at 29 °C, then at 25 °C, and finally at 20 °C. It was found that a gradual decrease in operational temperature allowed the nitrogen-converting community in the granules to acclimate, ensuring efficient nitrification even at ambient temperature (20 °C). Ammonium was fully removed from leachate regardless of the temperature, but higher operational temperatures resulted in higher ammonium removal rates [up to 44.2 mg/(L h) at 29 °C]. Lowering the operational temperature from 29 to 20 °C decreased nitrite accumulation in the GSBR cycle. The highest efficiency of total nitrogen removal was achieved at 25 °C (36.8 ± 10.9 %). The COD removal efficiency did not exceed 50 %. Granules constituted 77, 80 and 83 % of the biomass at 29, 25 and 20 °C, respectively. Ammonium was oxidized by both aerobic and anaerobic ammonium-oxidizing bacteria. Accumulibacter sp., Thauera sp., cultured Tetrasphaera PAO and Azoarcus–Thauera cluster occurred in granules independent of the temperature. Lower temperatures favored the occurrence of denitrifiers of Zooglea lineage (not Z. resiniphila), bacteria related to Comamonadaceae, Curvibacter sp., Azoarcus cluster, Rhodobacter sp., Roseobacter sp. and Acidovorax spp. At lower temperatures, the increased abundance of denitrifiers compensated for the lowered enzymatic activity of the biomass and ensured that nitrogen removal at 20 °C was similar to that at 25 °C and significantly higher than removal at 29 °C.     

Wax Removal and Diamondback Moth Performance in Collards Cultivars

The diamondback moth Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) is an herbivorous specialist on Brassicaceae species. Brassicas spp. plants developed a range of defenses (chemical, physical, and morphological) to prevent herbivores attack. In this study, we reported the antixenotic and antibiotic effects of outermost layer of two species of epicuticular wax of Brassicaceae, Brassica oleracea L. var. “Santo Antônio,” and Hybrid Kope F1 100MX, on larvae and adult of P. xylostella. In the choice experiment, P. xylostella adults showed an oviposition preference for collard cultivars Santo Antônio (control) and Hybrid Kope F1 100MX with wax removal. In the no-choice experiment, oviposition was 6.4 times higher in the Hybrid Kope F1 100MX with wax removal than without wax removal. There were significant differences among larvae feeding on leaf disks of Hybrid Kope F1 100MX in the treatments with (65.3 mg) and without wax removal (23.5 mg). The net reproduction rate (R ₀ ), and intrinsic (rm) and finite rates of increase (λ) of P. xylostella in the cv. Santo Antônio were bigger in the treatment without wax removal (R ₀  = 50.4, rm = 0.23 and λ = 1.26) than treatment with wax removal (R ₀  = 28.5, rm = 0.20 and λ = 1.22). However, only the R ₀ value was affected by mechanical wax removal in the Hybrid Kope F1 100MX (with wax removal R ₀  = 43.3 and without wax removal R ₀  = 30.8). In conclusion, the results indicate that collard’s wax is important to accessibility and development of P. xylostella, and its removal changes the resistance of collard’s varieties to P. xylostella.     

Does allelopathy affect co-culturing <Emphasis Type="Italic">Haslea ostrearia</Emphasis> with other microalgae relevant to aquaculture?

Haslea ostrearia is a marine diatom known to produce marennine, a water-soluble blue-green pigment responsible for the greening of oysters in ponds along the French Atlantic coast. This phenomenon occurs seasonally when H. ostrearia blooms in oyster ponds, and it increases the economic value of cultured oysters. From an ecological perspective, H. ostrearia blooms are accompanied by a decrease in the abundance of other microalgae, suggesting that this diatom produces allelochemicals. Recent studies showed that purified marennine has other biological activities, for instance antioxidant, antibacterial, and antiviral activities, which could be used in aquaculture to promote this pigment as a natural antipathogen agent. One important issue regarding the possible use of H. ostrearia in aquaculture as a mixed algal diet, however, is the importance of marennine allelopathy. In this study, we investigated the allelopathic effect of H. ostrearia on the growth of five microalgal species relevant to aquaculture: Chaetoceros calcitrans, Skeletonema costatum, Phaeodactylum tricornutum, Tetraselmis suecica, and Tisochrysis lutea. Allelopathic tests were realized by co-culturing these microalgae with H. ostrearia in batch and in semi-continuous mode, based on initial biovolume ratios. Our findings showed that inhibition of the growth of microalgae due to the presence of H. ostrearia and marennine was species dependent. Skeletonema costatum, C. calcitrans, and T. lutea were significantly more sensitive, whereas T. suecica and P. tricornutum appeared to be more resistant. Growth irradiance significantly influenced the allelopathic effect against the sensitive species S. costatum, and the H. ostrearia production of marennine increases with irradiance. Data presented in this study partly support the hypothesis that marennine released into the culture medium possibly acts as an allelochemical compound, thus explaining the dominance of H. ostrearia and the loss of sensitive algae in oyster ponds, but also that some species are insensitive, which allows co-culturing and use in a mixed algal diet in aquaculture.     

Consortium of Higher Aquatic Plants and Microalgae Designed to Purify Sewage of Heavy Metal Ions

We selected higher aquatic plants (HAP) and microalgae possessing a high sorption capacity in respect to heavy metals to form a consortium designed to purify contaminated aquatic ecosystems. Accumulation of heavy metals Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ was investigated in plants Pistia stratiotes, Elodea canadensis, and Lemna minor and green microalgae Chlorella vulgaris ВВ-2, Ankistrodesmus sp. ВI-1, Chlamydomonas reinhardtii В-4, and Scеnеdеsmus quadricauda В-1. It was found that intense accumulation of metals occurs in cultures of HAP Pistia stratiotes and Elodea canadensis. These plants are macroconcentrators of zinc, lead, and copper and microconcentrators of cadmium. Out of the examined cultures of microalgae, effective bioaccumulators of heavy metals were C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1. It was shown that heavy metals are selectively taken up from the medium in the series Zn²⁺ > Cu²⁺ > Cd²⁺ > Pb²⁺. In order to produce a consortium of higher aquatic plants and microalgae for purification of polluted aquatic ecosystems, we investigated interaction of HAP P. stratiotes and E. canadensis with microalgae C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1 in the course of their cocultivation. Neutral relations were detected between the cells of microalgae C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1 and HAP E. canadensis. At the same time, the cells of Ankistrodesmus sp. ВI-1 and HAP P. stratiotes formed a symbiosis. Microscopic examination showed numerous points where the cells of microalgae Ankistrodesmus sp. ВI-1 were attached to the roots of P. stratiotes plants. We tested an opportunity to employ the association between P. stratiotes and Ankistrodesmus sp. ВI-1 for purification of simulated wastewater polluted with heavy metal ions. This consortium proved to be capable of eliminating contaminants from the sewage, reducing their level in the sewage to standard values, and active accumulation of heavy metal ions.     

Effect of microalgae hydrolysate foliar application (<Emphasis Type="Italic">Arthrospira platensis</Emphasis> and <Emphasis Type="Italic">Scenedesmus</Emphasis> sp.) on <Emphasis Type="Italic">Petunia x hybrida</Emphasis> growth

In horticultural practice accelerated plant development and particularly earlier flowering, has been reported with microalgae applications. Therefore, the objective of this work was to study the effects of foliar spraying with Scenedesmus sp. and Arthrospira platensis hydrolysates on Petunia x hybrida plant development and leaf nutrient status. Three treatments were tested: T1 (foliar application with water, the control), T2 (foliar application with Arthrospira), and T3 (foliar application with Scenedesmus). Foliar spraying was applied five times (0, 14, 28, 35, and 42 days after transplanting). The concentration of both microalgae was 10 g L^?1. At the end of the trial biometric parameters and nutrient concentration in photosynthetic organs (the leaves) were measured. The results of this assay show that foliar application of Scenedesmus accelerated plant development in terms of higher rates of root growth, leaf and shoot development, and earliness of flowering. Arthrospira enhanced the root dry matter, the number of flowers per plant, and the water content. Nevertheless, a reduction was found in the conductive tissue (stem + petiole) dry weight with Arthrospira compared with Scenedesmus and the control. The results also show that microalgae hydrolysate supply can improve the plant nutrient status. Based on these results, it is advisable to use Scenedesmus hydrolysates in foliar applications to increase the blooming of Petunia x hybrida.     

The contribution of leaching to nutrient release from leaf litter of two emergent tree species in a Malaysian tropical peat swamp forest

Ostracode faunas changed in Lake Bonneville as the lake rose in the closed basin and became more dilute, then overflowed, and eventually returned to closed-basin hydrology; alkalinity (carbonate + bicarbonate) increased throughout the lake history. Fossil-ostracode faunas in marl deposited in the lake between about 30 and 13 cal ka allow reconstruction of these geochemical changes (as shown by R. M. Forester), and permit stratigraphic correlations within the large lake basin, including into the Sevier subbasin, which was connected to the main body of the lake but had different inflowing rivers. The first ostracode to appear in Lake Bonneville deposits at low altitudes is Limnocythere staplini; it was replaced by L. ceriotuberosa as the lake got larger and the water became more dilute and alkaline. Candona adunca and several species of Fabaeformiscandona mark the freshest-water phases. Cytherissa lacustris appeared in lake-margin settings after lake level dropped and cold, fresh groundwater began to discharge into the lake. Candona sp. cf. eriensis lived in the Sevier subbasin during the transgressive phase of the lake, but did not appear in the main body until late in the regressive phase. Limnocythere sappaensis, which requires high alkalinity, showed up late in the regressive phase in the main body when lake level was very low.     

An alternative strategy for enhancing lipid accumulation in chlorophycean microalgae for biodiesel production

Oleaginous microalgae are considered as important feedstocks for production of biodiesel. Under nutrient stress conditions, microalgae have the ability to accumulate higher amount of lipids, which can be transesterified for the production of biodiesel. In the present investigation, four different phosphate application strategies were examined in five green microalgae (Tetradesmus obliquus, Tetradesmus lagerheimii, Chlorella vulgaris, Chlorella minutissima, and Chlamydomonas sp.) to achieve higher lipid productivity. Effects of those strategies such as phosphate-sufficient (Control), phosphate-starved approach (PSA), biphasic phosphate-starved approach (BPSA), and sequential phosphate addition (SPA) were studied under batch culture mode. The BPSA emerging as the best in terms of lipid productivity consisted of two biomass harvesting phases, which would lead to an increase in the overall cost of biodiesel production. On the other hand, the SPA with a 1/200th dose of N 11 medium, i.e., 0.4 mg L^?1 of phosphate application in 3-day intervals, also resulted into higher lipid productivity which was equal to BPSA. Fatty acid composition of the biodiesel obtained from the microalgae was analyzed and the fuel characteristics were also evaluated. A profound (~14-fold) reduction in phosphorus requirements under the SPA mode with higher lipid productivity ensured qualitative biodiesel production and a lesser amount of phosphorus release, thus making the process eco-friendly.     

Bioflocculants’ production in a biomass-degrading bacterium using untreated corn stover as carbon source and use of bioflocculants for microalgae harvest

Background

Bioflocculation has been developed as a cost-effective and environment-friendly method to harvest multiple microalgae. However, the high production cost of bioflocculants makes it difficult to scale up. In the current study, low-cost bioflocculants were produced from untreated corn stover by a biomass-degrading bacterium Pseudomonas sp. GO2.

Results

Pseudomonas sp. GO2 showed excellent production ability of bioflocculants through directly hydrolyzing various biomasses. The untreated corn stover was selected as carbon source for bioflocculants’ production due to its highest flocculating efficiency compared to that when using other biomasses as carbon source. The effects of fermentation parameters on bioflocculants’ production were optimized via response surface methodology. According to the optimal model, an ideal flocculating efficiency of 99.8% was obtained with the fermentation time of 130.46 h, initial pH of 7.46, and biomass content of 0.64%. The relative importance of carboxymethyl cellulase and xylanase accounted for 51.8% in the process of bioflocculants’ production by boosted regression tree analysis, further indicating that the bioflocculants were mainly from the hydrolysates of biomass. Biochemical analysis showed that it contained 59.0% polysaccharides with uronic acid (34.2%), 32.1% protein, and 6.1% nucleic acid in the bioflocculants, which had an average molecular weight as 1.33 × 10⁶ Da. In addition, the bioflocculants showed the highest flocculating efficiency at a concentration of 12.5 mg L^?1 and were stable over broad ranges of pH and temperature. The highest flocculating efficiencies obtained for Chlorella zofingiensis and Neochloris oleoabundans were 77.9 and 88.9%, respectively.

Conclusions

The results indicated that Pseudomonas sp. GO2 can directly utilize various untreated lignocellulolytic biomasses to produce low-cost bioflocculants, which showed the high efficiency to harvest two green microalgae in a low GO2 fermentation broth/algal culture ratio.

     

Identification of Microalgae by Laser Desorption/Ionization Mass Spectrometry Coupled with Multiple Nanomatrices

In this study, we demonstrate a simple method to identify microalgae by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using three different substrates: HgSe, HgTe, and HgTeSe nanostructures. The fragmentation/ionization processes of complex molecules in algae varied according to the heat absorption and transfer efficiency of the nanostructured matrices (NMs). Therefore, the mass spectra obtained for microalgae showed different patterns of m/z values for different NMs. The spectra contained both significant and nonsignificant peaks. Constructing a Venn diagram with the significant peaks obtained for algae when using HgSe, HgTe, and HgTeSe NMs in m/z ratio range 100–1000, a unique relationship among the three sets of values was obtained. This unique relationship of sets is different for each species of microalgae. Therefore, by observing the particular relationship of sets, we successfully identified different algae such as Isochrysis galbana, Emiliania huxleyi, Thalassiosira weissflogii, Nannochloris sp., Skeletonema cf. costatum, and Tetraselmis chui. This simple and cost-effective SALDI-MS analysis method coupled with multi-nanomaterials as substrates may be extended to identify other microalgae and microorganisms in real samples.

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Graphical Abstract Identification of microalgae by surface-assisted laser desorption/ionization mass spectrometry coupled with three different mercury-based nanosubstrates