Benzoic acid

2.1.1 Chemicals. The chemicals used for PHB extraction (trichloromethane (≥ 99%), 1propanol (99.7%), benzoic acid (≥ 99.5%), and hydrochloric acid (37% w/v)) and for the culture medium preparation were acquired from PanReac AppliChem (Spain), except KNO 3 , which was purchased from COFARCAS (Spain). Poly(3hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with a mole fraction 3HB/3HV of 88/12 (≥ 99.99%) was acquired from Sigma-Aldrich (USA). O 2 (≥ 99.5%), CH 4 (≥ 99.995%), He (≥ 99.5%), and a synthetic biogas mixture containing 70% of CH 4 and 30% of CO 2 were provided by Abelló Linde S.A. (Spain).

All chemicals were analytical reagent or high purity grade. Thymolphthalein, phenolphthalein, potassium hydroxide, benzoic acid, starch, sodium thiosulfate, sodium sulfate anhydrous, acetic acid glacial, chloroform, cyclohexane, ethanol 96％, diethyl ether and isooctane were acquired from Panreac (Barcelona, Spain) . p-Anisidine was supplied by Sigma (Sigma-Aldrich, St. Louis, MO) .

Mineral salt medium containing nitrogen in the form of potassium nitrate (hereinafter referred to as NMS), or alternatively nitrogen free mineral salt medium (NFMS), were used. Nitrogen concentration was modified depending on the nitrogen supplementation strategy of each test series. Unless otherwise stated, the NMS (pH 6.8) contained (per liter of distilled water): KNO All chemicals above mentioned and reagents/solvents for PHB analysis (chloroform ≥99%, 1-propanol 99.7%, hydrochloric acid 37% w/v and benzoic acid ≥99.5% as internal standard) were purchased from PanReac AppliChem (Spain) unless otherwise specified. Potassium nitrate was obtained from COFARCAS (Spain). Poly(3-hydroxybutyrateco-3-hydroxyvalerate) (PHBV) with a 3HB fraction of 88% was provided by Sigma-Aldrich (USA). Synthetic biogas (70/30% v/v CH 4 :CO 2 ), oxygen (≥99.5%) and methane (≥99.995%) were supplied by Abelló Linde S.A. (Spain). Since methanotrophic growth and PHA accumulation has been already demonstrated under the presence of H 2 S, this minor biogas contaminant was not included in the mixture to avoid operational problems (López et al., 2018) (link).