Boreal forest soils function as a terrestrial net sink in the global carbon cycle. The prevailing dogma has focused on aboveground plant litter as a principal source of soil organic matter. Using C-14 bomb-carbon modeling, we show that 50 to 70% of stored carbon in a chronosequence of boreal forested islands derives from roots and root-associated microorganisms. Fungal biomarkers indicate impaired degradation and preservation of fungal residues in late successional forests. Furthermore, 454 pyrosequencing of molecular barcodes, in conjunction with stable isotope analyses, highlights root-associated fungi as important regulators of ecosystem carbon dynamics. Our results suggest an alternative mechanism for the accumulation of organic matter in boreal forests during succession in the long-term absence of disturbance.

http://science.sciencemag.org/content/sci/339/6127/1615.full.pdf

Roots and associated fungi drive long-term carbon sequestration in boreal forest.

Astaxanthin is a carotenoid widely used in salmonid and crustacean aquaculture to provide the pink color characteristic of that species. This application has been well documented for over two decades and is currently the major market driver for the pigment. Additionally, astaxanthin also plays a key role as an intermediary in reproductive processes. Synthetic astaxanthin dominates the world market but recent interest in natural sources of the pigment has increased substantially. Common sources of natural astaxanthin are the green algae Haematococcus pluvialis, the red yeast, Phaffia rhodozyma, as well as crustacean byproducts. Astaxanthin possesses an unusual antioxidant activity which has caused a surge in the nutraceutical market for the encapsulated product. Also, health benefits such as cardiovascular disease prevention, immune system boosting, bioactivity against Helycobacter pylori, and cataract prevention, have been associated with astaxanthin consumption. Research on the health benefits of astaxanthin is very recent and has mostly been performed in vitro or at the pre-clinical level with humans. This paper reviews the current available evidence regarding astaxanthin chemistry and its potential beneficial effects in humans.

Astaxanthin: a review of its chemistry and applications.

The marine environment represents a relatively untapped source of functional ingredients that can be applied to various aspects of food processing, storage, and fortification. Moreover, numerous marine-based compounds have been identified as having diverse biological activities, with some reported to interfere with the pathogenesis of diseases. Bioactive peptides isolated from fish protein hydrolysates as well as algal fucans, galactans and alginates have been shown to possess anticoagulant, anticancer and hypocholesterolemic activities. Additionally, fish oils and marine bacteria are excellent sources of omega-3 fatty acids, while crustaceans and seaweeds contain powerful antioxidants such as carotenoids and phenolic compounds. On the basis of their bioactive properties, this review focuses on the potential use of marine-derived compounds as functional food ingredients for health maintenance and the prevention of chronic diseases.

https://www.mdpi.com/1660-3397/9/6/1056/pdf

Marine Bioactives as Functional Food Ingredients: Potential to Reduce the Incidence of Chronic Diseases

The ketocarotenoid astaxanthin can be found in the microalgae Haematococcus pluvialis, Chlorella zofingiensis, and Chlorococcum sp., and the red yeast Phaffia rhodozyma. The microalga H. pluvialis has the highest capacity to accumulate astaxanthin up to 4–5% of cell dry weight. Astaxanthin has been attributed with extraordinary potential for protecting the organism against a wide range of diseases, and has considerable potential and promising applications in human health. Numerous studies have shown that astaxanthin has potential health-promoting effects in the prevention and treatment of various diseases, such as cancers, chronic inflammatory diseases, metabolic syndrome, diabetes, diabetic nephropathy, cardiovascular diseases, gastrointestinal diseases, liver diseases, neurodegenerative diseases, eye diseases, skin diseases, exercise-induced fatigue, male infertility, and HgCl2-induced acute renal failure. In this article, the currently available scientific literature regarding the most significant activities of astaxanthin is reviewed.

Potential health‐promoting effects of astaxanthin: A high‐value carotenoid mostly from microalgae

Microalgae metabolites: A rich source for food and medicine

Carotenoid composition in the green microalga Chlorococcum

Separation and determination of secoisolariciresinol diglucoside oligomers and their hydrolysates in the flaxseed extract by high-performance liquid chromatography

Simultaneous determination of free ergosterol and ergosteryl esters in Cordyceps sinensis by HPLC

A gradient reversed-phase high-performance liquid chromatography (HPLC) method was developed for the rapid determination of free ergosterol, ergosteryl esters, and ergocalciferol. The HPLC method was used to evaluate the distribution of ergosterol and ergosteryl esters in the different parts (stipe, pileus, and gills) of the agaric fungi, Agrocybe aegerita, Termitomyces albuminosus, and Lentinus edodes, and the relative changes of free and esterified ergosterols during the degradation of ergosterol in the comminuted fungal tissues. The results showed that total ergosterol levels and the relative abundances of free to esterified ergosterols were different among the various species and in the different parts of these agaric fungi. The results also indicated that ergosteryl esters were more stable than free ergosterol. While the content of free ergosterol markedly decreased, substantial amounts of ergosteryl esters remained for a long period, and even an increase in the contents of ergosteryl esters was also found in some comminuted fungal tissues. Therefore, it is possible that free ergosterol in the cell membrane of the dead fungal hyphae undergoes degradation or esterification, by which excess free ergosterol may be removed, and stored in cytosolic lipid particles. It is suggested that free ergosterol (not total ergosterol) should be used as a biomarker for fungal biomass.

Evaluation of ergosterol and its esters in the pileus, gill, and stipe tissues of agaric fungi and their relative changes in the comminuted fungal tissues.

Flaxseed is the richest dietary source of the lignan secoisolariciresinol diglucoside (SDG) and contains the largest amount of SDG oligomers, which are often hydrolyzed to break the ester linkages for the release of SDG and the glycosidic bonds for the release of secoisolariciresinol (SECO). The alkaline hydrolysis reaction kinetics of SDG oligomers from flaxseed and the acid hydrolysis process of SDG and other glucosides were investigated. For the kinetic modeling, a pseudo-first-order reaction was assumed. The results showed that the alkaline hydrolysis of SDG oligomers followed first-order reaction kinetics under mild alkaline hydrolytic conditions and that the concentration of sodium hydroxide had a strong influence on the activation energy of the alkaline hydrolysis of SDG oligomers. The results also indicated that the main acid hydrolysates of SDG included secoisolariciresinol monoglucoside (SMG), SECO, and anhydrosecoisolariciresinol (anhydro-SECO) and that the extent and the main hydrolysates of the acid hydrolysis reaction depended on the acid concentration, hydrolysis temperature, and time. In addition, the production and change of p-coumaric acid glucoside, ferulic acid glucoside and their methyl esters and p-coumaric acid, ferulic acid, and their methyl esters during the process of hydrolysis was also investigated.

Xin Liu

Papers

Carotenoid composition in the green microalga Chlorococcum

Separation and determination of secoisolariciresinol diglucoside oligomers and their hydrolysates in the flaxseed extract by high-performance liquid chromatography

Simultaneous determination of free ergosterol and ergosteryl esters in Cordyceps sinensis by HPLC

Evaluation of ergosterol and its esters in the pileus, gill, and stipe tissues of agaric fungi and their relative changes in the comminuted fungal tissues.

Hydrolysis kinetics of secoisolariciresinol diglucoside oligomers from flaxseed.