Uv 1900i double beam uv vis spectrophotometer

For pigment extraction, 2 mL of culture volume were harvested by centrifugation (14,500×g, 10 min, 4°C) and then submitted to mechanical lysis (TissueLyser LT, Qiagen, Les Ulis, France). Acid-washed glass beads (425-600 µm, Sigma-Aldrich, Saint-Quentin Fallavier, France) and a volume of 500 µL of 90% acetone were added to the pellet for a first cycle of lysis (50 Hz, 1 min). The extract was centrifuged (14,500×g, 5 min) and the supernatant collected in a new tube conserved on ice. Lysis cycles were then repeated with the addition of 500 µL of 90% acetone until the pellet became white. An absorbance spectrum between 400-800 nm was acquired from each final extract (UV 1900i double-beam UV-Vis Spectrophotometer, Shimadzu, Noisiel, France) and the chlorophyll a and chlorophyll c (c₁+c₂) concentrations were calculated according to Jeffrey and Humphrey (1975) (link). All chemicals were of analytical grade and obtained from Sigma-Aldrich (Saint Quentin Fallavier, France).

A Biobase BK-FD10 (Jinan, China) freeze-dryer was used to lyophilize MO leaves. A Pressurized Liquid Extraction (PLE) system (Fluid Management Systems, Inc., Watertown, MA, USA) was used to conduct all extractions. A Shimadzu UV-1900i Double-beam UV–Vis Spectrophotometer (Kyoto, Japan) was used for all spectrophotometric analyses. A Shimadzu CBM-20A liquid chromatograph and a Shimadzu SPD-M20A diode array detector (DAD) (Shimadzu Europa GmbH, Duisburg, Germany) were used for the quantification of individual polyphenols. The compounds were separated into a Phenomenex Luna C18(2) column from Phenomenex Inc. in Torrance, CA, USA, kept at 40 °C (100 Å, 5 μm, 4.6 mm × 250 mm). A colorimeter (Lovibond CAM-System 500, The Tintometer Ltd., Amesbury, UK) was used to determine CIELAB parameters (L*, a*, and b*) from the aqueous MO extracts.

Pyruvic acid was estimated spectrophotometrically through the method of Anthon and Barrett (2003) (link). Standards were prepared by using sodium pyruvate solution. The reading was carried out in a spectrophotometer at 515 nm using the UV-1900i UV-Vis double-beam spectrophotometer (SHIMADZU, Japan). Pyruvic acid was expressed as µmole g⁻¹ sample.