Screening design of nutritional and physicochemical parameters on bio-hydrogen and volatile fatty acids production from Citrus Peel Waste in batch reactors

Different nutritional and physicochemical conditions to obtain H2 from Citrus Peel Waste (CPW) were evaluated. For this, a screening design was carried out using Plackett and Burman design, in order to verify the main significant conditions of this process. The variables studied were pH (5.5–8.5), temperature (30–44 °C), autochthonous inoculum (0.75–2.25 gTVS.L−1), allochthonous inoculum (1–3 gTVS.L−1) and substrate (5–15 g.L−1), headspace (40–60%) and nutritional medium components, such as yeast extract (0–1 g.L−1), CaCO3, NaCl and peptone (0–5 g.L−1). The most significant operational variables were pH (8.5), allochthonous inoculum (3 gTVS.L−1) and substrate concentration (15 g CPW.L−1), conditions that favored the highest H2 (13.29 mmol.L−1) and acetic acid productions (1340 mg.L−1). Escherichia (34.5%) and Clostridium (29.93%) were the main genera identified under these conditions. [Display omitted] •Initial pH above 7.0 leads to acetic acid accumulation.•Acetogenesis is the main pathway related with CPW fermentation.•Yeast extract supplementation does not affect H2 production or rate from CPW.•Clostridium and Paraclostridium are the main genera involved in CPW fermentation.•Peptone supplementation can decrease the time for H2 production to get started.