Fungal enzyme sets for plant polysaccharide degradation

Enzymatic degradation of plant polysaccharides has many industrial applications, such as within the paper, food, and feed industry and for sustainable production of fuels and chemicals. Cellulose, hemicelluloses, and pectins are the main components of plant cell wall polysaccharides. These polysaccharides are often tightly packed, contain many different sugar residues, and are branched with a diversity of structures. To enable efficient degradation of these polysaccharides, fungi produce an extensive set of carbohydrate-active enzymes. The variety of the enzyme set differs between fungi and often corresponds to the requirements of its habitat. Carbohydrate-active enzymes can be organized in different families based on the amino acid sequence of the structurally related catalytic modules. Fungal enzymes involved in plant polysaccharide degradation are assigned to at least 35 glycoside hydrolase families, three carbohydrate esterase families and six polysaccharide lyase families. This mini-review will discuss the enzymes needed for complete degradation of plant polysaccharides and will give an overview of the latest developments concerning fungal carbohydrate-active enzymes and their corresponding families

Ferrotoroidic ground state in a heterometallic {Cr^IIIDy^III<inf>6</inf>} complex displaying slow magnetic relaxation

© 2017 The Author(s). Toroidal quantum states are most promising for building quantum computing and information storage devices, as they are insensitive to homogeneous magnetic fields, but interact with charge and spin currents, allowing this moment to be manipulated purely by electrical means. Coupling molecular toroids into larger toroidal moments via ferrotoroidic interactions can be pivotal not only to enhance ground state toroidicity, but also to develop materials displaying ferrotoroidic ordered phases, which sustain linear magneto-electric coupling and multiferroic behavior. However, engineering ferrotoroidic coupling is known to be a challenging task. Here we have isolated a {CrIIIDyIII6} complex that exhibits the much sought-after ferrotoroidic ground state with an enhanced toroidal moment, solely arising from intramolecular dipolar interactions. Moreover, a theoretical analysis of the observed sub-Kelvin zero-field hysteretic spin dynamics of {CrIIIDyIII6} reveals the pivotal role played by ferrotoroidic states in slowing down the magnetic relaxation, in spite of large calculated single-ion quantum tunneling rates

Oxygen Relieves the CO₂ and Acetate Dependency of <em>Lactobacillus johnsonii</em> NCC 533

<div><p>Oxygen relieves the CO₂ and acetate dependency of <i>Lactobacillus johnsonii</i> NCC 533. The probiotic <i>Lactobacillus johnsonii</i> NCC 533 is relatively sensitive to oxidative stress; the presence of oxygen causes a lower biomass yield due to early growth stagnation. We show however that oxygen can also be beneficial to this organism as it relieves the requirement for acetate and CO₂ during growth. Both on agar- and liquid-media, anaerobic growth of <i>L. johnsonii</i> NCC 533 requires CO₂ supplementation of the gas phase. Switching off the CO₂ supply induces growth arrest and cell death. The presence of molecular oxygen overcomes the CO₂ dependency. Analogously, <i>L. johnsonii</i> NCC 533 strictly requires media with acetate to sustain anaerobic growth, although supplementation at a level that is 100-fold lower (120 microM) than the concentration in regular growth medium for lactobacilli already suffices for normal growth. Analogous to the CO₂ requirement, oxygen supply relieves this acetate-dependency for growth. The <i>L. johnsonii</i> NCC 533 genome indicates that this organism lacks genes coding for pyruvate formate lyase (PFL) and pyruvate dehydrogenase (PDH), both CO₂ and acetyl-CoA producing systems. Therefore, C1- and C2- compound production is predicted to largely depend on pyruvate oxidase activity (POX). This proposed role of POX in C2/C1-generation is corroborated by the observation that in a POX deficient mutant of <i>L. johnsonii</i> NCC 533, oxygen is not able to overcome acetate dependency nor does it relieve the CO₂ dependency.</p> </div

Effect of CO₂ depletion on aerobic and anaerobic growth.

<p>Growth in stirred pH-controlled batch cultures sparged by N₂+5% CO₂ (closed symbols) or N₂+20% O₂+5% CO₂ (open symbols) as measured at OD₆₀₀. Data shown are the mean of at least two independent experiments ± standard error of the mean. In panel B, the gas regime was switched after 3 hours of exponential growth from a CO₂-rich gas to a CO₂-free gas: N₂ (closed symbols curve), N₂+20% O₂ (open symbols). Growth curves are the average ± standard deviation of triplicate experiments.</p