Environmental pollution from hazardous waste materials, organic pollutants and heavy metals, has adversely affected the natural ecosystem to the detriment of man. These pollutants arise from anthropogenic sources as well as natural disasters such as hurricanes and volcanic eruptions. Toxic metals could accumulate in agricultural soils and get into the food chain, thereby becoming a major threat to food security. Conventional and physical methods are expensive and not effective in areas with low metal toxicity. Bioremediation is therefore an eco-friendly and efficient method of reclaiming environments contaminated with heavy metals by making use of the inherent biological mechanisms of microorganisms and plants to eradicate hazardous contaminants. This review discusses the toxic effects of heavy metal pollution and the mechanisms used by microbes and plants for environmental remediation. It also emphasized the importance of modern biotechnological techniques and approaches in improving the ability of microbial enzymes to effectively degrade heavy metals at a faster rate, highlighting recent advances in microbial bioremediation and phytoremediation for the removal of heavy metals from the environment as well as future prospects and limitations. However, strict adherence to biosafety regulations must be followed in the use of biotechnological methods to ensure safety of the environment.

https://www.mdpi.com/1660-4601/14/12/1504/pdf

Microbial and Plant-Assisted Bioremediation of Heavy Metal Polluted Environments: A Review

/pdf/transformation-of-biomass-into-commodity-chemicals-using-2a93itd2a6.pdf

Transformation of biomass into commodity chemicals using enzymes or cells

Diatoms, a major group of photosynthetic microalgae, have a high biotechnological potential that has not been fully exploited because of the paucity of available genetic tools. Here we demonstrate targeted and stable modifications of the genome of the marine diatom Phaeodactylum tricornutum, using both meganucleases and TALE nucleases. When nuclease-encoding constructs are co-transformed with a selectable marker, high frequencies of genome modifications are readily attained with 56 and 27% of the colonies exhibiting targeted mutagenesis or targeted gene insertion, respectively. The generation of an enhanced lipid-producing strain (45-fold increase in triacylglycerol accumulation) through the disruption of the UDP-glucose pyrophosphorylase gene exemplifies the power of genome engineering to harness diatoms for biofuel production. Diatoms are photosynthetic microalgae with underutilized biotechnological potential. Here, the authors carry out targeted gene modifications of lipid metabolism genes in the diatom, Phaeodactylum tricornutum, resulting in a strain that exhibits a 45-fold increase in triacylglycerol accumulation.

/pdf/genome-engineering-empowers-the-diatom-phaeodactylum-12x66vglg4.pdf

Genome engineering empowers the diatom Phaeodactylum tricornutum for biotechnology

A wide range of lactic acid bacteria (LAB) is able to produce capsular or extracellular polysaccharides, with various chemical compositions and properties. Polysaccharides produced by LAB alter the rheological properties of the matrix in which they are dispersed, leading to typically viscous and “ropy” products. Polysaccharides are involved in several mechanisms such as prebiosis and probiosis, tolerance to stress associated to food process, and technological properties of food. In this paper, we summarize the beneficial properties of exopolysaccharides (EPS) produced by LAB with particular attention to prebiotic properties and to the effect of exopolysaccharides on the LAB-host interaction mechanisms, such as bacterial tolerance to gastrointestinal tract conditions, ability of ESP-producing probiotics to adhere to intestinal epithelium, their immune-modulatory activity, and their role in biofilm formation. The pro-technological aspect of exopolysaccharides is discussed, focusing on advantageous applications of EPS in the food industry, i.e., yogurt and gluten-free bakery products, since it was found that these microbial biopolymers positively affect the texture of foods. Finally, the involvement of EPS in tolerance to stress conditions that are commonly encountered in fermented beverages such as wine is discussed.

Exopolysaccharides produced by lactic acid bacteria: from health-promoting benefits to stress tolerance mechanisms

Layer-by-layer (LbL) was first introduced as a surface modification technique based on the sequential spontaneous adsorption of at least two distinct materials onto planar substrates. In the last two decades, this technique has been expanded to the coating of more convoluted geometries with high levels of tailored functionalization or with structural purposes. In this review, the potential uses of LbL films in biomedical engineering based mainly on the assembly of polyelectrolytes are reviewed. Examples of recent developments are provided, from the modification of substrates to improve their biointegration or to add specialized properties, to the three-dimensional extrapolation of this technique to more complex structures for cell seeding, drug delivery devices, biosensors and customizable microreactors. Future strategies and opportunities are compared with current medical and laboratorial methodologies. Through them, it is expected that LbL will contribute greatly to the development of new functional devices with high perspectives of return for the administration of active agents, supports for cells in regenerative medicine and tissue engineering, biosensing and construction of microtissues and disease models in the laboratory.

Polyelectrolyte multilayered assemblies in biomedical technologies

Microbial exopolysaccharides: Main examples of synthesis, excretion, genetics and extraction

Considering the demand from many industrial sectors, the production of microbial lipids constitutes an attractive topic for research. Oleaginous microorganisms can produce over 60% of their dry matter in single cell oils (SCOs), especially in the form of triglycerides (TAGs). Approximately forty microbial genera, especially yeasts and moulds, are known to be high lipid producers. Many abiotic factors, such as the culture conditions or nutriment availability, influence the production of microbial lipids that are of interest. Among the factors that can influence SCO production, the carbon source, limiting nutriments (especially nitrogen), pH and temperature are cited most often in the literature. Improvement in SCO production through the optimisation of abiotic factors encounters several limitations. Thus, research is currently increasingly oriented toward genetic modifications to optimise the synthesis of lipids by oleaginous microorganisms.

F. Donot

Papers

Microbial exopolysaccharides: Main examples of synthesis, excretion, genetics and extraction

Single cell oils (SCOs) from oleaginous yeasts and moulds: Production and genetics

Analysis of neutral lipids from microalgae by HPLC-ELSD and APCI-MS/MS