Biohydrogen and polyhydroxyalkanoates (PHA) as products of a two-steps bioprocess from deproteinized dairy wastes

In this study a two-steps bioprocess approach aimed at biohydrogen production via dark-fermentation, and polyhydroxyalkanoates-PHA production by mixed microbial cultures, was proposed to valorise two dairy-waste streams coming from cheese whey deproteinization (i.e. Ricotta cheese production and ultrafiltration). During the first step, the increase of OLR was tested, resulting in higher daily H2 volume (3.47 and 5.07 NL H2 d−1 for second cheese whey-SCW and concentrated cheese whey permeate-CCWP) and organic acids production (14.6 and 12.6 g L−1 d−1 for SCW and CCWP) for both the substrates, keeping good conversion of sugars into H2 (1.37 and 1.93 mol H2 mol−1 sugars for SCW and CCWP). During the second step, the organic acids were used for PHA production reaching high conversion yields for both the fermented streams (as average 0.74 ± 0.14 mg CODPHA mg−1 CODOA-in), with a maximum polymer content of 62 ± 4.5 and 55.1 ± 1.3% (g PHA g−1 VSS) for fermented SCW and fermented CCWP respectively. For the results reported, this study could be taken into consideration for larger scale application.