Production and characterisation of non-alcoholic beer using special yeast

Non-Saccharomyces yeast strains Saccharomycodes ludwigii, Schizosaccharomyces pombe, Lachancea fermentati and Pichia angusta together with a hybrid yeast strain cross-bred between genetically modified Saccharomyces cerevisiae W303-1A G418R and Saccharomyces eubayanus as well as the parent yeasts of the hybrid were studied for potential use for non-alcoholic beer production. The hybrid yeast, its Saccharomyces cerevisiae W303-1A G418R parent and Saccharomycodes ludwigii were not able to metabolise maltose during Durham tube tests. Schizosaccharomyces pombe, Lachancea fermentati and Pichia angusta metabolised maltose, however, showed limited ethanol production. Parameters, volatile and non-volatile organic compounds of beers produced by the studied yeast were analysed and compared to a beer produced by bottom fermented brewer’s yeast Saccharomyces pastorianus.

Structure of the mitochondrial ATP synthase from Pichia angusta determined by electron cryo-microscopy

The structure of the intact monomeric ATP synthase from the fungus, Pichia angusta, has been solved by electron cryo-microscopy. The structure provides insights into the mechanical coupling of the transmembrane proton motive force across mitochondrial membranes in the synthesis of ATP. This mechanism requires a strong and integral stator, consisting of the catalytic α3β3-domain, peripheral stalk, and, in the membrane domain, subunit a and associated supernumerary subunits, kept in contact with the rotor turning at speeds up to 350 Hz. The stator’s integrity is ensured by robust attachment of both the oligomycin sensitivity conferral protein (OSCP) to the catalytic domain and the membrane domain of subunit b to subunit a. The ATP8 subunit provides an additional brace between the peripheral stalk and subunit a. At the junction between the OSCP and the apparently stiff, elongated α-helical b-subunit and associated d- and h-subunits, an elbow or joint allows the stator to bend to accommodate lateral movements during the activity of the catalytic domain. The stator may also apply lateral force to help keep the static a-subunit and rotating c10-ring together. The interface between the c10-ring and the a-subunit contains the transmembrane pathway for protons, and their passage across the membrane generates the turning of the rotor. The pathway has two half-channels containing conserved polar residues provided by a bundle of four α-helices inclined at ∼30° to the plane of the membrane, similar to those described in other species. The structure provides more insights into the workings of this amazing machine.