A novel two-phase bioprocess for the production of Arthrospira (Spirulina) maxima LJGR1 at pilot plant scale during different seasons and for phycocyanin induction under controlled conditions.

A two-phase outdoor cultivation bioprocess for Arthrospira maxima LJGR1 combined with phycocyanin induction in concentrated cultures under controlled conditions was evaluated using a modified low-cost Zarrouk medium. Growth was monitored during 4 cycles in 2018 and 4 cycles in 2019. Biomass was harvested and concentrated using membrane technology at the end of each cycle for further phycocyanin induction using blue LED light (controlled conditions, 24 h). The highest biomass productivity was observed during spring and summer cycles (13.63-18.97 gDWm-2 d-1); during mid-fall and mid-end fall, a decrease was observed (9.93-7.76 gDWm-2 d-1). Under favorable growth conditions, phycocyanin induction was successful. However, during cycles with unfavorable growth condition, phycocyanin induction was not observed. Reactive-grade phycocyanin (3.72 ± 0.14) was recovered and purified using microfiltration and ultrafiltration technologies.

Biotransformation of water lettuce (Pistia stratiotes) to biohydrogen by Rhodopseudomonas palustris.

AIMS: Aim of the paper was to assess the feasibility of producing hydrogen as a biofuel by photofermentation of fermented water lettuce (Pistia stratiotes L.) waste biomass, after a nitrogen-stripping treatment. METHODS AND RESULTS: A natural (42OL) and an engineered strain (CGA676, with low-ammonium sensitivity) of Rhodopseudomonas palustris were used for producing hydrogen. The stripping procedure was highly effective for ammonium removal, with an acceptable selectivity (91% of ammonium was removed; only 14% of total organic acids were lost). Both strains were able to produce hydrogen only in the nitrogen-stripped substrate. The natural strain R. palustris 42OL showed a higher Biochemical Hydrogen Potential (1224 ml l-1 vs 720 ml l-1 ; 50·0 mol m-3 vs 29·4 mol m-3 ), but at a lower rate (5·6 ml l-1  h-1 vs 7·3 ml l-1  h-1 ; 0·23 mol m-3  h-1 vs 0·29 mol m-3  h-1 ) than strain CGA676. CONCLUSIONS: Water lettuce waste biomass can be used for biofuel production, after hydrolization, fermentation and nitrogen stripping. SIGNIFICANCE AND IMPACT OF THE STUDY: The investigation on novel, low cost and sustainable biomasses as feedstocks for biofuel production is a priority. Aquatic plants do not compete for arable land. Moreover, water lettuce is a floating and invasive weed, thus its biomass must be harvested when detrimental, and can now be biotransformed in clean hydrogen.

Introducing capnophilic lactic fermentation in a combined dark-photo fermentation process: a route to unparalleled H2 yields.

Two-stage process based on photofermentation of dark fermentation effluents is widely recognized as the most effective method for biological production of hydrogen from organic substrates. Recently, it was described an alternative mechanism, named capnophilic lactic fermentation, for sugar fermentation by the hyperthermophilic bacterium Thermotoga neapolitana in CO2-rich atmosphere. Here, we report the first application of this novel process to two-stage biological production of hydrogen. The microbial system based on T. neapolitana DSM 4359(T) and Rhodopseudomonas palustris 42OL gave 9.4 mol of hydrogen per mole of glucose consumed during the anaerobic process, which is the best production yield so far reported for conventional two-stage batch cultivations. The improvement of hydrogen yield correlates with the increase in lactic production during capnophilic lactic fermentation and takes also advantage of the introduction of original conditions for culturing both microorganisms in minimal media based on diluted sea water. The use of CO2 during the first step of the combined process establishes a novel strategy for biohydrogen technology. Moreover, this study opens the way to cost reduction and use of salt-rich waste as feedstock.

Gold biosorption by exopolysaccharide producing cyanobacteria and purple nonsulphur bacteria.

AIMS: This study was aimed at investigating the possible exploitation of phototrophic micro-organisms for the removal and the recovery of Au from Au-containing wastewaters deriving from a plating industry. METHODS AND RESULTS: A screening among ten phototrophic micro-organisms was carried out with pure solutions of Au to select the best strain in terms of metal uptake and selectivity. The direct use of the selected micro-organism on the Au-containing industrial wastewater was then carried out with the aim of assessing the potential of its use for the removal and the recovery of the precious metal from industrial wastewaters. CONCLUSIONS: This study showed the good potential of some exopolysaccharide-producing cyanobacteria as biosorbents for the recovery of Au from wastewaters of plating industries but also pointed out the need to design an efficient technology for the recovery of the metal from the biomass. SIGNIFICANCE AND IMPACT OF THE STUDY: The selection of good biosorbents for the recovery of gold from industrial wastewaters may open new perspectives to a green biotechnology so far considered too expensive for the mere treatment of wastewaters containing low valuable metals.

Capsular polysaccharides of cultured phototrophic biofilms.

Phototrophic biofilm samples from an Italian wastewater treatment plant were studied in microcosm experiments under varying irradiances, temperatures and flow regimes to assess the effects of environmental variables and phototrophic biomass on capsular exopolysaccharides (CPS). The results, obtained from circular dichroism spectroscopy and High Performance Liquid Chromatography, suggest that CPS have a stable spatial conformation and a complex monosaccharide composition. The total amount present was positively correlated with the biomass of cyanobacteria and diatoms, and negatively with the biovolume of green algae. The proportion of uronic acids showed the same correlation with these taxon groups, indicating a potential role of cyanobacteria and diatoms in the removal of residual nutrients and noxious cations in wastewater treatment. While overall biofilm growth was limited by low irradiance, high temperature (30 degrees C) and low flow velocity (25 l h(-1)) yielded the highest phototrophic biomass, the largest amount of CPS produced, and the highest proportion of carboxylic acids present.

Selectivity in the heavy metal removal by exopolysaccharide-producing cyanobacteria.

AIMS: The aim of this study was to assess the selective removal of Cu(II), Cr(III) and Ni(II) by strains of exopolysaccharide (EPS)-producing cyanobacteria, and to investigate the interaction of sorption in solutions with multiple-metals. METHODS AND RESULTS: Nine EPS-producing cyanobacteria were tested for their ability to remove Cr, Cu and Ni in both single- and multiple-metal solutions. In the single-metal solutions, some of the strains showed very high values of metal uptake, however, only two of them showed the capability to selectively remove one or two of the metals present in the multiple-metal solutions. In multi-metal systems, the binding process was either noninteractive, synergistic or competitive between metal ions for different strains of cyanobacteria. CONCLUSIONS: Cyanothece 16Som 2 showed significantly greater sorptive capacity for Cu (1.5-20x) and Cr (2-50x) than all other strains tested. The Nostoc PCC 7936 strain showed high specific and almost exclusive selectivity towards Cu, which suggests its use aimed at recovering this metal from multiple-metal solutions. SIGNIFICANCE AND IMPACT OF THE STUDY: To find out microbial sorbents with good metal selectivity may be very useful for building up processes aimed to recover valuable metals from industrial wastewaters.

Optimization of copper sorbing-desorbing cycles with confined cultures of the exopolysaccharide-producing cyanobacterium Cyanospira capsulata.

AIM: The aim of this study was to compare the copper removal capability of the exopolysaccharide-producing cyanobacterium Cyanospira capsulata confined into various filtering devices and to assess its reuse for several metal sorbing-desorbing cycles. METHODS AND RESULTS: C. capsulata cultures were confined into three dialysis devices and two hollow fibre systems with different surface to volume ratios. The maximum amount of Cu was removed by the biomass confined into dialysis cassettes, followed by the dialysis tubing systems and by the two hollow fibre devices. The experiments on the sorbing-desorbing cycles showed that, with the most effective desorbing agents, the same biomass can be utilized for eight consecutive sorbing-desorbing cycles. CONCLUSIONS: The efficiency of the metal removal process is directly related to a high surface to volume ratio of the confining system and the biomass can be utilized for multiple sorbing-desorbing cycles without significant loss in the metal removal efficiency. SIGNIFICANCE AND IMPACT OF STUDY: The feasibility of a metal removal process using EPS-producing cyanobacteria confined into filtering devices has been shown, pointing out the potential of this technique for industrial applications in the removal of metals from waste waters or in the recovery of valuable metals from water solutions.

Effectiveness of Cyanothece spp. and Cyanospira capsulata exocellular polysaccharides as antiadhesive agents for blocking attachment of Helicobacter pylori to human gastric cells.

The effect of cyanobacterial polysaccharides (from Cyanothece spp. and Cyanospira capsulata) on the binding of Helicobacter pylori to gastric epithelial cells was evaluated. The antiadhesive action on Kato III and HeLa S3 human gastric cell lines was established.

Generation of superoxide anion and SOD activity in haemocytes and muscle of American white shrimp (Litopenaeus vannamei) as a response to beta-glucan and sulphated polysaccharide.

Juvenile American white shrimp (Litopenaeus vannamei) were immersed in aerated beta-glucan and sulphated polysaccharide solutions for 1, 3 and 6 h. Superoxide anion and SOD activity in haemocytes and muscle were investigated to evaluate whether beta-glucan and sulphated polysaccharide induce any immunostimulatory activity. Haemocytes and muscle showed different levels of superoxide anion generation and SOD activity (2.0 and 14 times that of control, respectively) when shrimp were immersed for 6 h in aerated sea water containing beta-glucan and sulphated polysaccharide. Total haemocyte count (THC) decreased within the first 24 h after challenge with immunostimulants, but THC and total soluble haemocyte protein increased over normal values after 48-120 h. Single immunostimulation with beta-glucan and sulphated polysaccharide is capable of generating an increase in the respiratory burst of L. vannamei haemocytes.

Potential of unicellular cyanobacteria from saline environments as exopolysaccharide producers.

Fifteen Cyanothece strains isolated from saline environments have been characterized with regard to exopolysaccharide (EPS) production. The polymers contained six to eight monosaccharides, with one or two acidic sugars. In some EPS samples, the additional presence of acetyl, pyruvyl, and/or sulfate groups was also detected.

Occurrence of poly-beta-hydroxybutyrate in Spirulina species.

Several strains of photoautotrophically grown Spirulina spp. contained poly-beta-hydroxybutyrate (PHB) at concentrations never exceeding a few milligrams per gram of dry weight. Under mixotrophic growth conditions in the presence of acetate, PHB reached values greater than 2.5% of dry weight. With pyruvate, no significant effect on PHB accumulation was obtained.