Residual sugar from microalgae biomass harvested from phycoremediation of swine wastewater digestate.

The present study assessed the carbohydrate and sugar production from Chlorella spp. biomass harvested from a field scale reactor simulating phycoremediation of swine wastewater. The microalgae biomass was mainly composed by (%): carbohydrates (41 ± 0.4), proteins (50 ± 0.4), and lipids (1.3 ± 0.5). The residual sugar present in the biomass was extracted via acid hydrolysis. Among different concentrations of sulfuric acid tested (i.e., 47, 94, 188, 281 and 563 mM), significantly higher sugar content was obtained with 188 mM (0.496 g-sugar g-1 microalgae-DW). The concentration of sugar present in the microalgae did not differ significantly between the biomasses harvested by either centrifugation or coagulation-flocculation. Two commercially available strains of yeast (i.e., Saccharomyces cerevisiae and S. cerevisiae chardonnay) were tested for their capability to ferment sugar from lyophilized microalgae biomass. S. cerevisiae chardonnay showed a significantly faster consumption of sugar during the exponential growth phase. Both strains of yeast were capable of consuming most of the sugar added ≅ 8 g L-1 within 24 h. Overall, the results suggest that carbohydrate-rich microalgae biomass obtained from the phycoremediation of swine wastewaters can play an important role in green design for industries seeking alternative sources of feedstock rich in sugar.

Effects of Nitrogen and Phosphorus on Biochemical Composition of Microalgae Polyculture Harvested from Phycoremediation of Piggery Wastewater Digestate.

The effects of nitrogen (N) and/or phosphorus (P) starvation on the biochemical composition of native microalgae Chlorella spp. polyculture obtained from the phycoremediation of swine wastewaters were investigated. Microalgae-specific growth rate of 1.2 day(-1) was achieved (30.3 mg L(-1) day(-1)). PO4 (-2) and NH3 were completely removed from swine digestate effluent after 3 and 11 days, respectively. Microalgae harvested immediately after nutrient removal showed high protein (56-59 %) and carbohydrate (25-34 %) but low lipid (1.8-3 %) contents. Depletion of N or P alone stimulated carbohydrate production at the expenses of proteins. Significant lipid accumulation from 3 % ± 0.5 to 16.3 % ± 0.8 was reached only after 25 days following N and P starvation as demonstrated by Nile red-stained cells. Regarding to the effects of harvesting methods on cellular biochemical composition, circumstantial evidences indicate that coagulation-flocculation with tannin may lead to lower protein and lipid amounts but increased carbohydrate content (p < 0.01) as compared to centrifugation.

Enhancement of nutrient removal from swine wastewater digestate coupled to biogas purification by microalgae Scenedesmus spp.

This work investigated the effects of swine wastewater-derived biogas on microalgae biomass production and nutrient removal rates from piggery wastewater concomitantly with biogas filtration. Photobioreactors with dominant Scenedesmus spp. were prepared using non-sterile digestate and exposed to different photoperiods. In the presence of biogas and autotrophic conditions microalgae yield of 1.1±0.2 g L(-1) (growth rate of 141.8±3.5 mg L(-1) d(-1)) was obtained leading to faster N-NH3 and P-PO4(3-) assimilation rate of 21.2±1.2 and 3.5±2.5 mg L(-1) d(-1), respectively. H2S up to 3000 ppmv was not inhibitory and completely removed. Maximum CO2 assimilation of 219±4.8 mg L(-1) d(-1) was achieved. Biological consumption of CH4 up to 18% v/v was verified. O2 up to 22% v/v was controlled by adding acetate to exacerbate oxygen demand by microorganisms. Microalgae-based wastewater treatment coupled to biogas purification accelerates nutrient removal concomitantly producing valuable biomass and biomethane.

Biostimulation of anaerobic BTEX biodegradation under fermentative methanogenic conditions at source-zone groundwater contaminated with a biodiesel blend (B20).

Field experiments were conducted to assess the potential for anaerobic biostimulation to enhance BTEX biodegradation under fermentative methanogenic conditions in groundwater impacted by a biodiesel blend (B20, consisting of 20 % v/v biodiesel and 80 % v/v diesel). B20 (100 L) was released at each of two plots through an area of 1 m(2) that was excavated down to the water table, 1.6 m below ground surface. One release was biostimulated with ammonium acetate, which was added weekly through injection wells near the source zone over 15 months. The other release was not biostimulated and served as a baseline control simulating natural attenuation. Ammonium acetate addition stimulated the development of strongly anaerobic conditions, as indicated by near-saturation methane concentrations. BTEX removal began within 8 months in the biostimulated source zone, but not in the natural attenuation control, where BTEX concentrations were still increasing (due to source dissolution) 2 years after the release. Phylogenetic analysis using quantitative PCR indicated an increase in concentration and relative abundance of Archaea (Crenarchaeota and Euryarchaeota), Geobacteraceae (Geobacter and Pelobacter spp.) and sulfate-reducing bacteria (Desulfovibrio, Desulfomicrobium, Desulfuromusa, and Desulfuromonas) in the biostimulated plot relative to the control. Apparently, biostimulation fortuitously enhanced the growth of putative anaerobic BTEX degraders and associated commensal microorganisms that consume acetate and H2, and enhance the thermodynamic feasibility of BTEX fermentation. This is the first field study to suggest that anaerobic-methanogenic biostimulation could enhance source zone bioremediation of groundwater aquifers impacted by biodiesel blends.

In situ source zone sediment mixing coupled to groundwater biostimulation to enhance phenol natural attenuation.

Phenol is an industrially key compound that has a wide range of applications and also one of the most commonly found toxic pollutants in wastewaters and groundwater. This paper demonstrates the applicability of in situ remediation at a deactivated industrial site using source zone excavation and sediment mixing associated with nutrients delivery into groundwater. Sediment excavation and mixing displaced the entrapped source zone enhancing mass transfer into groundwater and contaminant bioavailability. A nutrient solution prepared with nitrate, phosphate, sodium hydroxide and hydrogen peroxide was continuously delivered into groundwater to stimulate biodegradation and restrict plume migration. The observed correlation between phenol-dependent Enterobacteriaceae concentrations throughout the remediation time frame supported circumstantial evidence of biodegradation. Phenol concentration in groundwater (up to 1,300 mg/L) was reduced >99% after 5 months following remediation and remained under the established site specific target level (4 mg/L). Nitrate and phosphate concentrations returned to background concentrations levels at the end of the remediation. Overall, the proposed in situ remediation scheme was effective to remediate this particular aquifer contaminated with phenol for over 20 years.

Indole-based assay to assess the effect of ethanol on Pseudomonas putida F1 dioxygenase activity.

Toluene dioxygenase (TDO) is ubiquitous in nature and has a broad substrate range, including benzene, toluene, ethylbenzene and xylenes (BTEX). Pseudomonas putida F1 (PpF1) induced on toluene is known to produce indigo from indole through the activity of TDO. In this work, a spectrophotometric assay previously developed to measure indole to indigo production rates was modified to characterize the effects of various ethanol concentrations on toluene aerobic biodegradation activity and assess catabolite repression of TDO. Indigo production rate by cells induced on toluene alone was 0.0012 +/- 0.0006 OD(610) min(-1). The presence of ethanol did not fully repress TDO activity when toluene was also available as a carbon source. However, indigo production rates by PpF1 grown on ethanol:toluene mixtures (3:1 w/w) decreased by approximately 50%. Overall, the proposed spectrophotometric assay is a simple approach to quantify TDO activity, and demonstrates how the presence of ethanol in groundwater contaminated with reformulated gasoline is likely to interfere with naturally occurring microorganisms from fully expressing their aerobic catabolic potential towards hydrocarbons bioremediation.