The effect of gradual increase in salinity on the biomass productivity and biochemical composition of several marine,halotolerant<Emphasis Type="Bold">,</Emphasis> and halophilic microalgae

Open ponds are the preferred cultivation system for large-scale microalgal biomass production. To be more sustainable, commercial scale biomass production should rely on seawater, as freshwater is a limiting resource, especially in places with high irradiance. If seawater is used for both pond fill and evaporative volume makeup, salinity of the growth media will rise over time. It is not possible for any species to achieve optimum growth over the whole saline spectrum (from seawater salinity level up to salt saturation state). In this study, we investigated the effects of gradual salinity increase (between 35 and 233 ppt) on biomass productivity and biochemical composition (lipid and carbohydrate) of six marine, two halotolerant, and a halophilic microalgae. A gradual and slow stepped salinity increase was found to expand the salinity tolerance range of tested species. A gradual reduction in biomass productivity and maximum photochemical efficiency was observed as a consequence of increased salinity in all tested species. Among the marine microalgae, Tetraselmis showed highest biomass productivity (32 mg L^?1 day^?1) with widest salinity tolerance range (35 to 109 ppt). Halotolerant Amphora and Navicula were able to grow from 35 ppt to 129 ppt salinity. Halophilic Dunaliella was the only species capable of growing between 35 and 233 ppt and showed highest lipid content (56.2%) among all tested species. This study showed that it should be possible to maintain high biomass in open outdoor cultivation utilizing seawater by growing Tetraselmis, Amphora, and Dunaliella one after another as salinity increases in the cultivation system.     

Cultivation of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> with swine wastewater and potential for algal biodiesel production

In this study, an alga-based simultaneous process of treating swine wastewater (SWW) and producing biodiesel was explored. Chlorella vulgaris (UTEX-265) was employed as a model species, and a SWW-based medium was prepared by dilution with tap water. Chlorella vulgaris grew well in the SWW-based medium, and at optimum dilution ratios, it exceeded the conventional culture medium in terms of biomass concentration and productivity. In eightfold diluted SWW, which supported the maximum growth, biomass productivity was 0.247 g L^?1 day^?1, while the productivity was merely 0.165 g L^?1 day^?1 in standard tris-acetate-phosphorous (TAP) algal medium. In addition, fatty acid methyl ester (FAME) productivity was greater in the SWW-based medium (0.067 versus 0.058 g L^?1 day^?1). This enhanced productivity resulted in more than 95 % removal of both nitrogen and phosphorous. All these show that C. vulgaris cultivation is indeed possible in a nutrient-rich wastewater with appropriate dilution, and in so doing, the wastewater can effectively be treated.     

Biological CO<Subscript>2</Subscript> fixation using C<Emphasis Type="Italic">hlorella vulgaris</Emphasis> and its thermal characteristics through thermogravimetric analysis

The present research is focused on cultivation of microalgae strain Chlorella vulgaris for bio-fixation of CO₂ coupled with biomass production. In this regard, a single semi-batch vertical tubular photobioreactor and four similar photobioreactors in series have been employed. The concentration of CO₂ in the feed stream was varied from 2 to 12 % (v/v) by adjusting CO₂ to air ratio. The amount of CO₂ capture and algae growth were monitored by measuring decrease of CO₂ concentration in the gas phase, microalgal cell density, and algal biomass production rate. The results show that 4 % CO₂ gives maximum amount of biomass (0.9 g L^?1) and productivity (0.118 g L^?1 day^?1) of C. vulgaris in a single reactor. In series reactors, average productivity per reactor found to be 0.078 g L^?1 day^?1. The maximum CO₂ uptake for single reactor also found with 4 % CO_2, and it is around 0.2 g L^?1 day^?1. In series reactors, average CO₂ uptake is 0.13 g L^?1 day^?1 per reactor. TOC analysis shows that the carbon content of the produced biomass is around 40.67 % of total weight. The thermochemical characteristics of the cultivated C. vulgaris samples were analyzed in the presence of air. All samples burn above 200 °C and the combustion rate become faster at around 600 °C. Almost 98 wt% of the produced biomass is combustible in this range.     

Process Engineering for High-Cell-Density Cultivation of Lipid Rich Microalgal Biomass of <Emphasis Type="Italic">Chlorella</Emphasis> sp. FC2 IITG

In the present study, process engineering strategy was applied to achieve lipid-rich biomass with high density of Chlorella sp. FC2 IITG under photoautotrophic condition. The strategy involved medium optimization, intermittent feeding of limiting nutrients, dynamic change in light intensity, and decoupling growth and lipid induction phases. Medium optimization was performed using combinations of artificial neural network or response surface methodology with genetic algorithm (ANN-GA and RSM-GA). Further, a fed-batch operation was employed to achieve high cell density with intermittent feeding of nitrate and phosphate along with stepwise increase in light intensity. Finally, mutually exclusive biomass and lipid production phases were decoupled into two-stage cultivation process: biomass generation in first stage under nutrient sufficient condition followed by lipid enrichment through nitrogen starvation. The key findings were as follows: (i) ANN-GA resulted in an increase in biomass titer of 157 % (0.95 g L^?1) in shake flask and 42.8 % (1.0 g L^?1) in bioreactor against unoptimized medium at light intensity of 20 μE m^?2 s^?1; (ii) further optimization of light intensity in bioreactor gave significantly improved biomass titer of 5.6 g L^?1 at light intensity of 250 μE m^?2 s^?1; (iii) high cell density of 13.5 g L^?1 with biomass productivity of 675 mg L^?1 day^?1 was achieved with dynamic increase in light intensity and intermittent feeding of limiting nutrients; (iv) finally, two-phase cultivation resulted in biomass titer of 17.7 g L^?1 and total lipid productivity of 313 mg L^?1 day^?1 which was highest among Chlorella sp. under photoautotrophic condition.     

Biomass productivity of two <Emphasis Type="Italic">Scenedesmus</Emphasis> strains cultivated semi-continuously in outdoor raceway ponds and flat-panel photobioreactors

Semi-continuous algal cultivation was completed in outdoor flat-panel photobioreactors (panels) and open raceway ponds (raceways) from February 17 to May 7, 2015 for side-by-side comparison of areal productivities at the Arizona Center for Algae Technology and Innovation in Mesa, AZ, USA. Experiments used two strains of Scenedesmus acutus (strains LB 0414 and LB 0424) to assess productivity, areal density, nutrient removal, and harvest volume across cultivation systems and algal strains. Panels showed an average biomass productivity of 19.0?±?0.6 g m^?2 day^?1 compared to 6.62?±?2.3 g m^?2 day^?1 for raceways. Photosynthetic efficiency ranged between 1.32 and 2.24 % for panels and between 0.30 and 0.68 % for raceways. Panels showed an average nitrogen consumption rate of 38.4?±?8.6 mg N L^?1 day^?1. Cultivation in raceways showed a consumption rate of 3.8?±?2.5 and 7.1?±?4.2 mg N L^?1 day^?1 for February/March and April/May, respectively, due to increase in biomass productivity. Excess nutrients were required to prevent a decrease in productivity. Daily biomass harvest volumes between 18 and 36 % from panels did not affect culture productivity, but density decreased with increased harvest volume. High cultivation temperatures above 30 °C caused strain LB 0414 to lyse and crash. Strain LB 0424 did not show any difference in biomass productivity when peak temperatures reached 34, 38, or 42 °C, but showed decreased productivity when the peak temperature during cultivation was 30 °C. Using algal strains with different temperature tolerances can generate increased annual biomass productivity.     

<Emphasis Type="Italic">Tetraselmis suecica</Emphasis> culture for CO<Subscript>2</Subscript> bioremediation of untreated flue gas from a coal-fired power station

The accumulation of atmospheric CO₂, primarily due to combustion of fossil fuels, has been implicated in potential global climate change. The high rate of CO₂ bioremediation by microalgae has emerged as a favourable method for reducing coal-fired power plant emissions. However, coal-fired power station flue gas contains other chemicals such as SO_x which can inhibit microalgal growth. In the current study, the effect of untreated flue gas as a source of inorganic carbon on the growth of Tetraselmis in a 1000 L industrial-scale split-cylinder internal-loop airlift photobioreactor was examined. The culture medium was recycled after each harvest. Tetraselmis suecica grew very well in this airlift photobioreactor during the 7-month experiment using recycled medium from an electroflocculation harvesting unit. Increased medium SO₄ ^2? concentration as high as 870 mg SO₄ ^2??L^?1 due to flue gas addition and media recycling had no negative effect on the overall growth and productivity of this alga. The potential organic biomass productivity and carbon sequestration using an industrial-scale airlift PBR at International Power Hazelwood, Gippsland, Victoria, Australia, are 178.9?±?30 mg L^?1 day^?1 and 89.15?±?20 mg?‘C’?L^?1 day^?1, respectively. This study clearly indicates the potential of growing Tetraselmis on untreated flue gas and using recycled medium for the purpose of biofuel and CO₂ bioremediation.     

Comparison of growth of Tetraselmis in a tubular photobioreactor (Biocoil) and a raceway pond

Microalgae cultivation systems can be divided broadly into open ponds and closed photobioreactors. This study investigated the growth and biomass productivity of the halophilic green alga Tetraselmis sp. MUR-233, grown outdoors in paddle wheel-driven open raceway ponds and in a tubular closed photobioreactor (Biocoil) at a salinity of 7 % NaCl (w/v) between mid-March and June 2010 (austral autumn/winter). Volumetric productivity in the Biocoil averaged 67 mg ash-free dry weight (AFDW) L^?1 day^?1 when the culture was grown without CO₂ addition. This productivity was 86 % greater, although less stable, than that achieved in the open raceway pond (36 mg L^?1 day^?1) grown at the same time in the autumn period. The Tetraselmis culture in the open raceway pond could be maintained in semi-continuous culture for the whole experimental period of 3 months without an additional CO₂ supply, whereas in the Biocoil, under the same conditions, reliable semi-continuous culture was only achievable for a period of 38 days. However, stable semi-continuous culture was achieved in the Biocoil by the addition of CO₂ at a controlled pH of ~7.5. With CO₂ addition, the volumetric biomass productivity in the Biocoil was 85 mg AFDW L^?1 day^?1 which was 5.5 times higher than the productivity achieved in the open raceway pond (15 mg AFDW L^?1 day^?1) with CO₂ addition and 8 times higher compared to the productivity in the open raceway pond without CO₂ addition (11 mg AFDW L^?1 day^?1), when cultures were grown in winter. The illuminated area productivities highlight an alternative story and showed that the open raceway pond had a three times higher productivity (3,000 mg AFDW m^?2 day^?1) compared to the Biocoil (850 mg AFDW m^?2 day^?1). Although significant differences were found between treatments and cultivation systems, the overall average lipid content for Tetraselmis sp. MUR-233 was 50 % in exponential phase during semi-continuous cultivation.     

Isolation and screening of euryhaline <Emphasis Type="Italic">Tetraselmis</Emphasis> spp. suitable for large-scale outdoor culture in hypersaline media for biofuels

Natural saline lakes in Western Australia were sampled for microalgae species and strains with potential for large-scale outdoor cultivation over a wide range of salinities for biofuels production. Using a rational isolation and screening process, several Tetraselmis strains (Chlorophyta, Chlorodendrales) with a broad range of salinity tolerance were identified and were characterised further for their potential for biofuels production. Specific growth rates increased from 0.8 to 1.2 days^?1 when the medium salinity was decreased from 11 to 3 % (w/v) NaCl (1.88 to 0.51 M NaCl) in batch cultivation mode, thereby indicating quick adaptation to large salinity changes. In general, ash-free dry weight (AFDW), total lipid, protein and carbohydrate contents per cell were highest in the early stages of growth. Salinity increases led to an increase in cell AFDW, with the highest mean maximum of 2555?±?659 pg AFDW.cell^?1 at 11 % (w/v) NaCl in the strains Tetraselmis MUR 167 and MUR 219 which had been in culture for many years, as compared to the mean maximum of 981?±?141 pg AFDW.cell^?1 the in newly isolated strains MUR 230, 231, 232 and 233. Similar observations on total lipid, protein and carbohydrate content per cell were made between the two groups of strains. Overall, all strains yielded high biomass and total lipid productivities over a very wide range of salinities without large variation in their gross biochemical composition and growth pattern. Based on AFDW and total lipid productivity data, the order of preference for selecting strains for further investigation for large-scale culture was MUR 231?>?MUR 233?>?MUR 219?>?MUR 230?>?MUR 232?>?MUR 167. The Tetraselmis spp. were also very competitive as shown by the outdoor cultivation of diatom, Halamphora coffeaeformis MUR 158, in parallel with Tetraselmis sp. MUR 167 which resulted in the diatom being outcompeted by the green alga. Our results demonstrate the high commercial potential of euryhaline Tetraselmis spp. for cultivation over a broad range of salinity in outdoor cultures.     

Productivity and biochemical composition of <Emphasis Type="Italic">Tetradesmus obliquus</Emphasis> and <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis>: effects of different cultivation approaches

The present work evaluated biomass productivity, carbon dioxide fixation rate, and biochemical composition of two microalgal species, Phaeodactylum tricornutum (Bacillariophyta) and Tetradesmus obliquus (Chlorophyta), cultivated indoors in high-technology photobioreactors (HT-PBR) and outdoors both in pilot ponds and low-technology photobioreactors in a greenhouse in southern Italy. Microalgae were grown in standard media, under nitrogen starvation, and in two liquid digestates obtained from anaerobic digestion of agro-zootechnical and vegetable biomass. P. tricornutum, cultivated in semi-continuous mode in indoor HT-PBRs with standard medium, showed a biomass productivity of 21.0?±?2.3 g m^?2 d^?1. Applying nitrogen starvation, the lipid productivity increased from 2.3 up to 4.5?±?0.5 g m^?2 d^?1, with a 24 % decrease of biomass productivity. For T. obliquus, a biomass productivity of 9.1?±?0.9 g m^?2 d^?1 in indoor HT-PBR was obtained using standard medium. Applying liquid digestates as fertilizers in open ponds, T. obliquus gave a biomass productivity (10.8?±?2.0 g m^?2 d^?1) not statistically different from complete medium such as P. tricornutum (6.5?±?2.2 g m^?2 d^?1). The biochemical data showed that the fatty acid composition of the microalgal biomass was affected by the different cultivation conditions for both microalgae. In conclusion, it was found that the microalgal productivity in standard medium was about doubled in HT-PBR compared to open ponds for P. tricornutum and was about 20 % higher for T. obliquus.     

Carbon dioxide and poultry waste utilization for production of polyhydroxyalkanoate biopolymers by <Emphasis Type="Italic">Nostoc muscorum</Emphasis> Agardh: a sustainable approach

The new paradigm is to view wastes as resources for sustainable development. In this regard, the feasibility of poultry waste and CO₂ utilization for cultivation of a filamentous nitrogen-fixing cyanobacterium, Nostoc muscorum Agardh, was investigated for production polyhydroxyalkanoates, the biodegradable polymers. This cyanobacterium showed profound rise in biomass yield with up to 10 % CO₂ supply in airstream with an aeration rate of 0.1 vvm. Maximum biomass yield of 1.12 g L^?1 was recorded for 8 days incubation period, thus demonstrating a CO₂ biofixation rate of 0.263 g L^?1 day^?1 at 10 % (v/v) CO₂-enriched air. Poultry litter (PL) supplementation also had a positive impact on the biomass yield. The nutrient removal efficiency of N. muscorum was reflected in the significant reduction in nutrient load of PL over the experimental period. A maximum poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) [P(3HB-co-3HV)] copolymer yield of 774 mg L^?1 (65 % of dry cell wt.), the value almost 11-fold higher than the control, was recorded in 10 g L^?1 PL-supplemented cultures with 10 % CO₂ supply under the optimized condition, thus demonstrating that N. muscorum has good potential for CO₂ biomitigation and poultry waste remediation while simultaneously producing eco-friendly polymers.     

Production of butanol and isopropanol with an immobilized <Emphasis Type="Italic">Clostridium</Emphasis>

Clostridium beijerinckii optinoii is a Clostridium species that produces butanol, isopropanol and small amounts of ethanol. This study compared the performances of batch and continuous immobilized cell fermentations, investigating how media flow rates and nutritional modification affected solvent yields and productivity. In 96-h batch cultures, with 80 % of the 30 g L^?1 glucose consumed in synthetic media, solvent concentration was 9.45 g L^?1 with 66.0 % as butanol. In a continuous fermentation using immobilized C. beijerinckii optinoii cells, also with 80 % of 30 g L^?1 glucose utilization, solvent productivity increased to 1.03 g L^?1 h^?1. Solvent concentration reached 12.14 g L^?1 with 63.0 % as butanol. Adjusting the dilution rate from 0.085 to 0.050 h^?1 to allow extended residence time in column was required when glucose concentration in fresh media was increased from 30 to 50 g L^?1. When acetate was used to improve the buffer capacity in media, the solvent concentration reached 12.70 on 50 g L^?1 glucose. This continuous fermentation using immobilized cells showed technical feasibility for solvent production.     

Interspecific biodiversity enhances biomass and lipid productivity of microalgae as biofuel feedstock

Large improvements in biomass and lipid production are required to make massive scale algal biodiesel production an economic reality. The application of the biodiversity strategy to enhance algal biomass as biofuel feedstock is little. The algal diversity was manipulated in this study to investigate the effects of a combination of biodiversity complementarity and a new medium consisting of seawater and agricultural fertilizer on lipid productivity. The algae diverse community includes two strains of Dunaliella salina (Dunaliella salina 19/30 and 19/18) and three species of Nannochloropsis (Nannochloropsis oculata, Nannochloropsis salina, and Nannochloropsis gaditana). The results showed that the most diverse community (5 species) produced an average of sixfold more biomass in the new medium than did the standard f/2 culture medium. The most diverse polyculture had the highest growth rate (1.01 day^?1), biomass (1.2 g L^?1), and lipid productivity (0.31 g L^?1 day^?1). The assessment of algal polycultures relative to monocultures is particularly interesting and novel for this biofuel field, and the observations that these polycultures resulted in significant lipid productivity improvements are very useful addition to the biofuel research. The possible mechanism (resource diversity) to explain the synergy in mixed cultures warrants further investigation.     

Maximizing the productivity of the microalgae <Emphasis Type="Italic">Scenedesmus</Emphasis> AMDD cultivated in a continuous photobioreactor using an online flow rate control

In this study, production of the microalga Scenedesmus AMDD in a 300 L continuous flow photobioreactor was maximized using an online flow (dilution rate) control algorithm. To enable online control, biomass concentration was estimated in real time by measuring chlorophyll-related culture fluorescence. A simple microalgae growth model was developed and used to solve the optimization problem aimed at maximizing the photobioreactor productivity. When optimally controlled, Scenedesmus AMDD culture demonstrated an average volumetric biomass productivity of 0.11 g L^?1 d^?1 over a 25 day cultivation period, equivalent to a 70 % performance improvement compared to the same photobioreactor operated as a turbidostat. The proposed approach for optimizing photobioreactor flow can be adapted to a broad range of microalgae cultivation systems.     

Bicarbonate-based carbon capture and algal production system on ocean with floating inflatable-membrane photobioreactor

This study aims to develop a low-cost microalgae culture system which uses a simple closed vessel as photobioreactor to save manufacturing cost, waves for mixing to save energy cost, and high concentration of bicarbonate for carbon supply to avoid the high cost of CO₂-bubbling pipeline construction on the ocean as well as to control pH by buffering the effect of bicarbonate/carbonate. To test this idea, the alkalihalophilic cyanobacterium Euhalothece sp. was cultured with 1.0 M NaHCO₃ in small-scale floating photobioreactors (PBRs) on 10-cm-high artificial waves at first. The final biomass concentration was up to 0.91 and 1.47 g L^?1 for indoor and outdoor cultures, respectively. However, the recorded dissolved oxygen (DO) was occasionally over-saturated (> 500% of air saturation), indicating mass transfer problem. k _L a in these PBRs with different culture depth was measured then, and the results showed great variation, from 0.13 to 4.87 h^?1. At the scale of 1.0 m², this floating PBR was made with low-cost membrane and inflatable design. It was placed on the ocean surface and mixed with natural waves. Biomass concentration of 1.63 g L^?1 and productivity of 8.27 g m^?2 day^?1 were obtained in this culture. With these results, the feasibility of a low-cost microalgae culture system was proven, which could systematically reduce the cost of photobioreactor manufacturing, operating, and maintenance.     

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.     

Energetic evaluation of an internally illuminated photobioreactor for algal cultivation

An annular internally illuminated photobioreatcor (IIPBR) configuration based on the airlift/bubble column principles was developed and validated at an 18 l prototype scale using Scenedemus sp. and Nannochloropsis salina in batch and semi-continuous modes, at constant light supply and constant gas-to-culture volume ratio, but at varying CO₂-to-air ratios. Highest biomass production was recorded at CO₂-to-air ratio of 4% with Scenedesmus sp. and at 1% with Nannochloropsis salina. The energetic performance of this IIPBR was quantified in terms of biomass productivity per unit energy input, P/E (g W^?1 day^?1), considering energy input for illumination and for pneumatic mixing and circulation. Under optimal conditions, the IIPBR evaluated in this study achieved P/E of 1.42 g W^?1 day^?1 for Scenedesmus sp. and P/E of 0.34 g W^?1 day^?1 for Nannochloropsis salina. These P/E values are better than those estimated for airlift and bubble column photobioreactor configurations reported in the literature.     

Characterization of cell structural change,growth, lipid accumulation,and pigment profile of a novel oleaginous microalga, <Emphasis Type="Italic">Vischeria stellata</Emphasis> (Eustigmatophyceae), cultured with different initial nitrate supplies

The appropriate microalgal species and the optimal nitrogen supply in culture medium are vital factors in maximizing biomass and metabolite productivities in microalgae. Vischeria stellata is an edaphic unicellular eustigmatophycean microalga. Cytological and ultrastructural characteristics and the effects of different initial nitrate-nitrogen concentrations on growth, lipid accumulation, fatty acid profile, and pigment composition were investigated in the present study. The cell structures of V. stellata changed with the degree of nutrient utilization and growth phase. The initial nitrate concentration for the optimal growth of V. stellata ranged from 6.0 to 9.0 mM. The maximum total lipid (TLs), neutral lipid (NLs), and total fatty acid (TFAs) contents were 55.9, 51.9, and 44.7 % of dry biomass, respectively. The highest volumetric productivity of TLs, NLs, and TFAs reached 0.28, 0.25, and 0.21 g L^?1 day^?1, respectively. V. stellata had a suitable fatty acid profile for biodiesel production, as well as containing eicosapentaenoic acid (EPA) for nutraceutical applications. In addition, the content β-carotene, increased gradually as culture time was prolonged, resulting in its exclusive production at the end of cultivation. V. stellata is a promising microalgal strain for the production of biofuels and bioproducts.     

Enhanced citric acid production by a yeast <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> over-expressing a pyruvate carboxylase gene

In this study, after the expression of a pyruvate carboxylase gene (PYC) cloned from Meyerozyma guilliermondii in a marine-derived yeast Yarrowia lipolytica SWJ-1b, a transformant PG86 obtained had much higher PYC activity than Y. lipolytica SWJ-1b. At the same time, the PYC gene expression and citric acid (CA) production by the transformant PG86 were also greatly enhanced. When glucose concentration in the medium was 60.0 g L^?1, CA concentration formed by the transformant PG86 was 34.02 g L^?1, leading to a CA yield of 0.57 g g^?1 of glucose. During a 10-L fed-batch fermentation, the final concentration of CA was 101.0 ± 1.3 g L^?1, the yield was 0.89 g g^?1 of glucose, the productivity was 0.42 g L^?1 h^?1 and only 5.93 g L^?1 reducing sugar was left in the fermented medium within 240 h of the fed-batch fermentation. HPLC analysis showed that most of the fermentation products were CA.     

Biomass and terpenoids produced by mutant strains of <Emphasis Type="Italic">Arthrospira</Emphasis> under low temperature and light conditions

The filamentous Cyanobacterium Arthrospira is commercially produced and is a functional, high-value, health food. We identified 5 low temperature and low light intensity tolerant strains of Arthrospira sp. (GMPA1, GMPA7, GMPB1, GMPC1, and GMPC3) using ethyl methanesulfonate mutagenesis and low temperature screening. The 5 Arthrospira strains grew rapidly below 14?°C, 43.75 μmol photons m^?2 s^?1 and performed breed conservation at 2.5?°C, 8.75 μmol photons m^?2 s^?1. We used morphological identification and molecular genetic analysis to identify GMPA1, GMPA7, GMPB1 and GMPC1 as Arthrospira platensis, while GMPC3 was identified as Arthrospira maxima. Growth at different culture temperatures was determined at regular intervals using dry biomass. At 16?°C and 43.75 μmol photons m^?2 s^?1, the maximum dry biomass production and the mean dry biomass productivity of GMPA1, GMPB1, and GMPC1 were 2057?±?80 mg l^?1, 68.7?±?2.5 mg l^?1 day^?1, 1839?±?44 mg l^?1, 60.6?±?1.8 mg l^?1 day^?1, and 2113?±?64 mg l^?1, 77.7?±?2.5 mg l^?1 day^?1 respectively. GMPB1 was chosen for additional low temperature tolerance studies and growth temperature preference. In winter, GMPB1 grew well at mean temperatures <10?°C, achieving 3258 mg dry biomass from a starting 68 mg. In summer, GMPB1 grew rapidly at mean temperatures more than 28?°C, achieving 1140 mg l^?1 dry biomass from a starting 240 mg. Phytonutrient analysis of GMPB1 showed high levels of C-phycocyanin and carotenoids. Arthrospira metabolism relates to terpenoids, and the methyl-d-erythritol 4-phosphate pathway is the only terpenoid biosynthetic pathway in Cyanobacteria. The 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) gene from GMPB1 was cloned and phylogenetic analysis showed that GMPB1 is closest to the Cyanobacterium Oscillatoria nigro-viridis PCC711. Low temperature tolerant Arthrospira strains could broaden the areas suitable for cultivation, extend the seasonal cultivation time, and lower production costs.     

Sweet Sorghum Juice and Bagasse as Feedstocks for the Production of Optically Pure Lactic Acid by Native and Engineered <Emphasis Type="Italic">Bacillus coagulans</Emphasis> Strains

Sweet sorghum is a bioenergy crop that produces large amounts of soluble sugars in its stems (3–7 Mg ha^?1) and generates significant amounts of bagasse (15–20 Mg ha^?1) as a lignocellulosic feedstock. These sugars can be fermented not only to biofuels but also to bio-based chemicals. The market potential of the latter may be higher given the current prices of petroleum and natural gas. The yield and rate of production of optically pure d-(?)- and l-(+)-lactic acid as precursors for the biodegradable plastic polylactide was optimized for two thermotolerant Bacillus coagulans strains. Strain 36D1 fermented the sugars in unsterilized sweet sorghum juice at 50 °C to l-(+)-lactic acid (～150 g L^?1; productivity, 7.2 g L^?1 h^?1). B. coagulans strain QZ19-2 was used to ferment sorghum juice to d-(?)-lactic acid (～125 g L^?1; productivity, 5 g L^?1 h^?1). Carbohydrates in the sorghum bagasse were also fermented after pretreatment with 0.5 % phosphoric acid at 190 °C for 5 min. Simultaneous saccharification and co-fermentation of all the sugars (SScF) by B. coagulans resulted in a conversion of 80 % of available carbohydrates to optically pure lactic acid depending on the B. coagulans strain used as the microbial biocatalyst. Liquefaction of pretreated bagasse with cellulases before SScF (L + SScF) increased the productivity of lactic acid. These results show that B. coagulans is an effective biocatalyst for fermentation of all the sugars present in sweet sorghum juice and bagasse to optically pure lactic acid at high titer and productivity as feedstock for bio-based plastics.