Inhibition of anaerobic digestion process: A review

Because of the high catalytic activities and substrate specificity, natural enzymes have been widely used in industrial, medical, and biological fields, etc. Although promising, they often suffer from intrinsic shortcomings such as high cost, low operational stability, and difficulties of recycling. To overcome these shortcomings, researchers have been devoted to the exploration of artificial enzyme mimics for a long time. Since the discovery of ferromagnetic nanoparticles with intrinsic horseradish peroxidase-like activity in 2007, a large amount of studies on nanozymes have been constantly emerging in the next decade. Nanozymes are one kind of nanomaterials with enzymatic catalytic properties. Compared with natural enzymes, nanozymes have the advantages such as low cost, high stability and durability, which have been widely used in industrial, medical, and biological fields. A thorough understanding of the possible catalytic mechanisms will contribute to the development of novel and high-efficient nanozymes, and the rational regulations of the activities of nanozymes are of great significance. In this review, we systematically introduce the classification, catalytic mechanism, activity regulation as well as recent research progress of nanozymes in the field of biosensing, environmental protection, and disease treatments, etc. in the past years. We also propose the current challenges of nanozymes as well as their future research focus. We anticipate this review may be of significance for the field to understand the properties of nanozymes and the development of novel nanomaterials with enzyme mimicking activities.

Nanozymes: Classification, Catalytic Mechanisms, Activity Regulation, and Applications

The molecular mechanisms controlling synaptogenesis in the central nervous system (CNS) are poorly understood. Previous reports showed that a glia-derived factor strongly promotes synapse development in cultures of purified CNS neurons. Here, we identify this factor as cholesterol complexed to apolipoprotein E-containing lipoproteins. CNS neurons produce enough cholesterol to survive and grow, but the formation of numerous mature synapses demands additional amounts that must be provided by glia. Thus, the availability of cholesterol appears to limit synapse development. This may explain the delayed onset of CNS synaptogenesis after glia differentiation and neurobehavioral manifestations of defects in cholesterol or lipoprotein homeostasis.

https://science.sciencemag.org/content/sci/294/5545/1354.full.pdf

CNS synaptogenesis promoted by glia-derived cholesterol

Amongst the diverse and potent biological activities of free fatty acids (FFAs) is the ability to kill or inhibit the growth of bacteria. The antibacterial properties of FFAs are used by many organisms to defend against parasitic or pathogenic bacteria. Whilst their antibacterial mode of action is still poorly understood, the prime target of FFA action is the cell membrane, where FFAs disrupt the electron transport chain and oxidative phosphorylation. Besides interfering with cellular energy production, FFA action may also result from the inhibition of enzyme activity, impairment of nutrient uptake, generation of peroxidation and auto-oxidation degradation products or direct lysis of bacterial cells. Their broad spectrum of activity, non-specific mode of action and safety makes them attractive as antibacterial agents for various applications in medicine, agriculture and food preservation, especially where the use of conventional antibiotics is undesirable or prohibited. Moreover, the evolution of inducible FFA-resistant phenotypes is less problematic than with conventional antibiotics. The potential for commercial or biomedical exploitation of antibacterial FFAs, especially for those from natural sources, is discussed.

/pdf/antibacterial-free-fatty-acids-activities-mechanisms-of-5ew888s9bz.pdf

Antibacterial free fatty acids: activities, mechanisms of action and biotechnological potential

Thematic review series: brain Lipids. Cholesterol metabolism in the central nervous system during early development and in the mature animal.

There is provided a food-grade microbicidal or microbiostatic composition containing a food or food-grade material and as the primary microbicide a mono-ester of a polyol and a twelve carbon atom aliphatic fatty acid.

Fatty acids and derivatives of antimicrobial agents

Over 40 natural or synthetic lipophilic compounds were screened for antimicrobial activity. Gram (+) bacteria and yeasts but not Gram (-) bacteria were affected by these agents. Epimino and selena fatty acids are more active than their corresponding straight chain unsubstituted fatty acids. The position of selenium influenced the antimicrobial activity of the fatty acids. The presence and position of a double or triple bond, usually an important factor in long chain fatty acids (greater than C14) had little or no effect in C11 fatty acids. Optimum antimicrobial activity was found for fatty acids and their corresponding monoglycerides when the chain lenght was C12. The dilaurin derivative was not active.

Antimicrobial lipids: Natural and synthetic fatty acids and monoglycerides

A broth dilution method was used to determine the minimal inhibitory concentration of a series of fatty acid esters of polyhydric alcohols against gram-negative and gram-positive organisms. Gram-negative organisms were not affected. Gram-positive organisms were inhibited as follows. Of the monoglycerol esters, monoglycerol laurate was the most active. Esters of polyglycerols (tri-, hexa-, and decaglycerol esters) were generally active when the fatty acid had chain lengths of 8 to 12 carbon atoms. Sucrose esters, when active, except for laurate, are more active than the free fatty acid. The spectrum of antimicrobial action of esters of polyhydric alcohols is narrower when compared with the free acids.

/pdf/antimicrobial-action-of-esters-of-polyhydric-alcohols-4opqvjlig8.pdf

Antimicrobial action of esters of polyhydric alcohols.

Lipids as Host-Resistance Factors of Human Milk

Publisher Summary This chapter presents a critical review of brain cholesterol metabolism. Modern aspects of brain sterol metabolism are reviewed by Davison and Kabara. Consequently, for this review, the chapter emphasizes only the more recent concepts of brain cholesterol metabolism. To form a backdrop for the discussion of brain cholesterol metabolism, the anatomical and chemical changes taking place in the central nervous system (CNS) during growth and development are outlined in the chapter. Because sex, nutrition, precursor used, diurnal variation, etc., influence biosynthetic rates as measured, their influence should be considered in any developmental analysis of metabolic capacity within the CNS. Whole brain values obtained in the past from animals injected with a radioactive precursor did not reflect metabolism or changes in metabolism of anatomical areas, individual cells or organelles. Although accurate information is not available, conclusions based on such comparisons lead to statements in the literature which are very difficult to change, even in the face of new and more conclusive data.

Jon J. Kabara

Papers

Fatty acids and derivatives of antimicrobial agents

Antimicrobial lipids: Natural and synthetic fatty acids and monoglycerides

Antimicrobial action of esters of polyhydric alcohols.

Lipids as Host-Resistance Factors of Human Milk

A critical review of brain cholesterol metabolism