Multidisciplinary integrated characterization of a native Chlorella-like microalgal strain isolated from a municipal landfill leachate

Extraction methods of algae oils for the production of third generation biofuels - A review

Microalgae are the main source of third-generation biofuels because they have a lipid content of 20-70%, can be abundantly produced and do not compete in the food market besides other benefits. Biofuel production from microalgae is a promising option to contribute for the resolution of the eminent crisis of fossil energy and environmental pollution specially in the transporting sector. The choice of lipid extraction method is of relevance and associated to the algae morphology (i.e., rigid cells). Therefore, it is essential to develop suitable extraction technologies for economically viable and environment-friendly lipid recovery processes with the aim of achieving a commercial production of biofuels from this biomass. This review presents an exhaustive analysis and discussion of different methods and processes of lipid extraction from microalgae for the subsequent conversion to biodiesel. Physical methods based on the use of supercritical fluids, ultrasound and microwaves were reviewed. Chemical methods using solvents with different polarities, aside from mechanical techniques such as mechanical pressure and enzymatic methods, were also analyzed. The advantages, drawbacks, challenges and future prospects of lipid extraction methods from microalgae have been summarized to provide a wide panorama of this relevant topic for the production of economic and sustainable energy worldwide.

Trends in digital image processing of isolated microalgae by incorporating classification algorithm

Identification of microalgae species is of importance due to the uprising of harmful algae blooms affecting both the aquatic habitat and human health. Despite this occurence, microalgae have been identified as a green biomass and alternative source due to its promising bioactive compounds accumulation that play a significant role in many industrial applications. Recently, microalgae species identification has been conducted through DNA analysis and various microscopy techniques such as light, scanning electron, transmission electron, and atomic force -microscopy. The aforementioned procedures have encouraged researchers to consider alternate ways due to limitations such as costly validation, requiring skilled taxonomists, prolonged analysis, and low accuracy. This review highlights the potential innovations in digital microscopy with the incorporation of both hardware and software that can produce a reliable recognition, detection, enumeration, and real-time acquisition of microalgae species. Several steps such as image acquisition, processing, feature extraction, and selection are discussed, for the purpose of generating high image quality by removing unwanted artifacts and noise from the background. These steps of identification of microalgae species is performed by reliable image classification through machine learning as well as deep learning algorithms such as artificial neural networks, support vector machines, and convolutional neural networks. Overall, this review provides comprehensive insights into numerous possibilities of microalgae image identification, image pre-processing, and machine learning techniques to address the challenges in developing a robust digital classification tool for the future.

Application of Five Different Chlorella sp. Microalgal Strains for the Treatment of Vegetation Waters Derived from Unconventional Oil Extractions Enriched with Citrus Byproducts

The Mediterranean diet has, among its cornerstones, the use of olive oil for its nutraceutical and organoleptic properties. Despite the numerous merits, olive-oil mill wastewater (OMWW), which is generated by the olive-oil extraction process, is one of the most serious environmental pollutants in the Mediterranean countries. The polluting potential of OMWW is due to its high content of tannins, polyphenols, polyalcohols, pectins and lipids. In order to close the recovery cycle of a fortified citrus olive oils previously developed, we tested the ability of five microalgae of the Chlorella group (SEC_LI_ChL_1, CL_Sc, CL_Ch, FB and Idr) in lowering the percentage of total phenolic compounds in vegetation water. This was obtained with three different extraction processes (conventional, and lemon and orange peels) at three concentrations each (10%, 25% and 50%). The results showed that strains Idr, FB and CL_Sc from the Lake Massaciuccoli can tolerate vegetation water from conventional and lemon peel extractions up to 25%; these strains can also reduce the phenolic compounds within the tests. The application of microalgae for OMWW treatment represents an interesting opportunity as well as an eco-friendly low-cost solution to be developed within companies as a full-scale approach, which could be applied to obtain a fortified microalgal biomass to be employed in nutraceutical fields.

Evaluation of Nutraceutical Properties of Eleven Microalgal Strains Isolated from Different Freshwater Aquatic Environments: Perspectives for Their Application as Nutraceuticals

The increasing global population and the simultaneous growing attention to natural, sustainable, and healthier products are driving the food industry towards research on alternative food sources. In this scenario, microalgae are gaining worldwide attention as "functional feedstocks" for foods, feeds, supplements, and nutraceutical formulations, being a source of high-value metabolites including polyphenols and other antioxidant compounds. In this work, eleven microalgal strains from freshwater environments were evaluated for their nutraceutical properties, focusing on photosynthetic pigments, total polyphenols, and flavonoid content, as well as in vitro antioxidant activities. Data helped to select those strains showing the most promising features for simultaneous massive growth and bioactive compound production. Results highlighted that the microalgae have variable values for both biochemical parameters and antioxidant activities, mainly depending on the solvents and applied treatment rather than on the isolation sources or the phylogenetic attribution. According to our results, the putative best candidates for massive cultivation under laboratory conditions for the simultaneous extraction of different molecules with nutraceutical potential are strains F1 (Scenedesmaceae), F3 (Chlamydomonas debariana), R1 (Chlorella sorokiniana), and C2 (Chlorella-like).