ISMAI

About: ISMAI is a facility organization based out in Maia, Portugal. It is known for research contribution in the topics: Population & Aerobic exercise. The organization has 228 authors who have published 424 publications receiving 8515 citations. The organization is also known as: Instituto Univeristário da Maia.

Light requirements in microalgal photobioreactors: an overview of biophotonic aspects

Abstract: In order to enhance microalgal growth in photobioreactors (PBRs), light requirement is one of the most important parameters to be addressed; light should indeed be provided at the appropriate intensity, duration, and wavelength. Excessive intensity may lead to photo-oxidation and -inhibition, whereas low light levels will become growth-limiting. The constraint of light saturation may be overcome via either of two approaches: increasing photosynthetic efficiency by genetic engineering, aimed at changing the chlorophyll antenna size; or increasing flux tolerance, via tailoring the photonic spectrum, coupled with its intensity and temporal characteristics. These approaches will allow an increased control over the illumination features, leading to maximization of microalgal biomass and metabolite productivity. This minireview briefly introduces the nature of light, and describes its harvesting and transformation by microalgae, as well as its metabolic effects under excessively low or high supply. Optimization of the photosynthetic efficiency is discussed under the two approaches referred to above; the selection of light sources, coupled with recent improvements in light handling by PBRs, are chronologically reviewed and critically compared.

Microalgae as sources of high added-value compounds--a brief review of recent work.

Abstract: Microalgae have found commercial applications as natural sources of valuable macromolecules, including carotenoids, long-chain polyunsaturated fatty acids, and phycocolloids. As photoautotrophs, their simple growth requirements make them attractive for bioprocesses aimed at producing high added-value compounds that are in large demand by the pharmaceutical market. A few compounds synthesized by microalgae have indeed proven to possess anti-inflammatory, antiviral, antimicrobial, and antitumoral features; astaxanthin, a known antioxidant produced by Haematococcus pluvialis, is an illustrative example with important anti-inflammatory and antitumoral roles. From a chemical standpoint, several such compounds are polysaccharides or long chain fatty acids, where the latter can be either saturated or unsaturated. Additionally, their chemical structures are often atypical, whereas their concentrations can exceed those found in many other natural sources. The productivity and biochemical composition of microalgae depend strongly on the mode of cultivation, medium composition, and nutrient profile. Consequently, numerous efforts aimed at elucidating the practical impacts of the aforementioned parameters have been developed. This review accordingly covers the knowledge produced in the last two decades on the uses of microalgae to obtain physiologically active compounds, and on the optimization of the underlying production and purification processes. It also identifies major gaps and opportunities in this field that should be addressed or exploited in the near future.

Metal uptake by microalgae: Underlying mechanisms and practical applications

Abstract: Metal contamination of a few aquatic, atmospheric, and soil ecosystems has increased ever since the industrial revolution, owing to discharge of such elements via the effluents of some industrial facilities. Their presence to excessive levels in the environment will eventually lead to serious health problems in higher animals owing to accumulation throughout the food web. Current physicochemical methods available for recovery of metal pollutants (e.g., chemical precipitation, oxidation/reduction, or physical ion exchange) are either expensive or inefficient when they are present at very low concentrations. Consequently, removal of toxic metals by microorganisms has emerged as a potentially more economical alternative. Microalgae (in terms of both living and nonliving biomass) are an example of microorganisms suitable to recover metals and able to attain noteworthy percent removals. Their relatively high metal-binding capacities arise from the intrinsic composition of their cell walls, which contain negatively charged functional groups. Consequently, microalgal cells are particularly efficient in uptake of those contaminants when at low levels. Self-defense mechanisms developed by microalgal cells to survive in metal-containing media and environmental factors that affect their removal (e.g., pH, temperature, and biomass concentration) are reviewed here in a comprehensive way and further discussed in attempts to rationalize this form of remediation vis-a-vis with conventional nonbiological alternatives.