Utilizing CO2 in industrial off-gas for microalgae cultivation: considerations and solutions.

The utilization of microalgae to treat carbon dioxide (CO2)-rich industrial off-gas has been suggested as both beneficial for emissions reduction and economically favorable for the production of microalgal products. Common sources of off-gases include coal combustion (2-15% CO2), cement production (8-15% CO2), coke production (18-23% CO2), and ore smelting (6-7% CO2). However, industrial off-gas also commonly contains other acid gas components [typically nitrogen oxides (NOX) and sulfur dioxide (SO2)] and metals that could inhibit microalgae growth and productivity. To utilize industrial off-gas effectively in microalgae cultivation systems, a number of solutions have been proposed to overcome potential inhibitions. These include bioprospecting to identify suitable strains, genetic modification to improve specific cellular characteristics, chemical additions, and bioreactor designs and operating procedures.In this review, results from microalgae experiments related to utilizing off-gas are presented, and the outcomes of different conditions discussed along with potential solutions to resolve limitations associated with the application of off-gas.

Dark stress for improved lipid quantity and quality in bioprospected acid-tolerant green microalgae.

The cost of microalgae cultivation is one of the largest limitations to achieving sustainable, large-scale microalgae production of commercially desirable lipids. Utilizing CO2 as a 'free' carbon source from waste industrial flue gas emissions can offer wide-ranging cost savings. However, these gas streams typically create acidic environments, in which most microalgae cannot survive due to the concentration of CO2 and the presence of other acidic gasses such as NO2 and SO2. To address this situation, we investigated growth of a mixed acid-tolerant green microalgal culture (91% dominated by a single Coccomyxa sp. taxon) bioprospected at pH 2.8 from an acid mine drainage impacted water body. The culture was grown at pH 2.5 and fed with a simulated flue gas containing 6% CO2 and 94% N2. On reaching the end of the exponential growth phase, the culture was exposed to either continued light-dark cycle conditions or continual dark conditions. After three days in the dark, the biomass consisted of 28% of lipids, which was 42% higher than at the end of the exponential phase and 55% higher than the maximum lipid content achieved under light/dark conditions. The stress caused by being continually in the dark also favoured the production of omega-3 and omega-6 polyunsaturated fatty acids (PUFAs; 19.47% and 21.04%, respectively, after 7 days) compared to 7-days of light-dark treatment (1.94% and 9.53%, respectively) and showed an increase in nitrogen content (C:N ratio of 6.4) compared to light-dark treatment (C:N ratio of 11.9). The results of the research indicate that use of acid tolerant microalgae overcomes issues using flue gasses that will create an acidic environment and that applying dark stress is a low-cost stressor stimulates production of desirable dietary lipids.

Nerve growth factor inhibitor with novel-binding domain demonstrates nanomolar efficacy in both cell-based and cell-free assay systems.

Nerve growth factor (NGF), a member of the neurotrophin family, is known to regulate the development and survival of a select population of neurons through the binding and activation of the TrkA receptor. Elevated levels of NGF have been associated with painful pathologies such as diabetic neuropathy and fibromyalgia. However, completely inhibiting the NGF signal could hold significant side effects, such as those observed in a genetic condition called congenital insensitivity to pain and anhidrosis (CIPA). Previous methods of screening for NGF-inhibitors used labeling techniques which have the potential to alter molecular interactions. SPR spectroscopy and NGF-dependent cellular assays were utilized to identify a novel NGF-inhibitor, BVNP-0197 (IC50  = 90 nmol/L), the first NGF-inhibitor described with a high nanomolar NGF inhibition efficiency. The present study utilizes molecular modeling flexible docking to identify a novel binding domain in the loop II/IV cleft of NGF.

Bioprospecting for acidophilic lipid-rich green microalgae isolated from abandoned mine site water bodies.

With fossil fuel sources in limited supply, microalgae show tremendous promise as a carbon neutral source of biofuel. Current microalgae biofuel strategies typically rely on growing high-lipid producing laboratory strains of microalgae in open raceways or closed system photobioreactors. Unfortunately, these microalgae species are found to be sensitive to environmental stresses or competition by regional strains. Contamination by invasive species can diminish productivity of commercial algal processes. A potential improvement to current strategies is to identify high-lipid producing microalgae, which thrive in selected culture conditions that reduce the risk of contamination, such as low pH. Here we report the identification of a novel high-lipid producing microalgae which can tolerate low pH growth conditions. Lig 290 is a Scenedesmus spp. isolated from a low pH waterbody (pH = 4.5) in proximity to an abandoned lignite mine in Northern Ontario, Canada. Compared to a laboratory strain of Scendesmus dimorphus, Lig 290 demonstrated robust growth rates, a strong growth profile, and high lipid production. As a consequence, Lig 290 may have potential application as a robust microalgal species for use in biofuel production.