Meso erythritol

To determine extracellular erythritol concentrations, supernatant samples of cultures were subjected to HPLC analysis. HPLC samples were either directly filtered or prepared by treating 500 μl supernatant sample with 50 μl of 35 % (v/v) perchloric acid (Merck), incubation on ice for 10 min and subsequent addition of 27 μl of 7 M KOH (Merck). After vortexing, the precipitate was removed by centrifugation for 5 min at 12,000 rpm and subsequent filtering (Sartorius Stedin Biotech, minisart SRP4, 0.45 μm). Separation of organic acids was achieved by application of a 20 μl aliquot on a Rezex ROA-Organic Acid H⁺ (8 %) HPLC column (Phenomenex), coupled to a refractive index detector (Jasco, RI-1530), using a flow of 0.5 ml/min and a column temperature of 85 °C. The concentration was determined by comparison of its peak size with known amounts of meso-erythritol (Sigma-Aldrich) and d-erythrose (Sigma-Aldrich).

All chemicals were of the highest available purity and purchased from Sigma‐Aldrich (St Louis, MO, USA), VWR (Radnor, PA, USA) and Roth (Karlsruhe, Germany). Primers were obtained from LGC Genomics (Vienna, Austria) or Sigma‐Aldrich. Restriction endonucleases, T4 DNA ligase and Phusion polymerase were obtained from Thermo Fisher Scientific Biosciences (St Leon‐Rot, Germany). GoTaq polymerase was purchased from Promega (Madison, WI, USA). Zeocin and the pPICZB vector were obtained from Invitrogen (Carlsbad, CA, USA). The 2‐keto‐GLC standard, meso‐erythritol, LC‐MS grade distilled water, ethoxylamine hydrochloride, water‐free pyridine and N‐methyl‐N‐(trimethylsilyl)trifluoroacetamide with 1% trimethylchlorosilane in water‐free pyridine were purchased from Sigma‐Aldrich.

Standard compounds of sugar as glycerol, meso-erythritol, xylose, arabinose, ribose, xylitol, arabitol, adonitol, fructose, mannose, glucose, mannitol, myo-inositol, sucrose, maltose, and reagents, i.e., N-methyl-N-(trimethylsilyl)-trifluoroacetamide (MSTFA), trimethylchlorosilane (TMCS), 2-methyl 3-heptanone were purchased from Sigma-Aldrich (St. Louis, MO, United States). Pyridine was obtained from Merck (Darmstadt, Germany), O-methylhydroxylamine hydrochloride from TCI (Tokyo, Japan), d27-myristic acid from CIL (Tewksbury, MA, United States), methanol from RCI Labscan (Bangkok, Thailand), fatty acid methyl ester (FAME) mixture was purchased from Agilent Technologies (Bangkok, Thailand), and n-alkanes mixture (C7-C40) from Supelco, Inc. (Bellefonte, PA, United States). Sodium chloride (Carlo Erba, Chaussée du Vexin, Val-de-Reuil, France) and a 120 μm DVB/CWR/PDMS SPME Arrow (CTC Analytics AG, Zwingen, Switzerland) were utilized for volatile extraction.