Carboxylates like volatile fatty acids (VFAs) can be produced by acidogenic fermentation (AF) of dairy wastes like cheese whey, a massive residue produced at 160.67 million m3of which 42% are not valorized and impact the environment. In mixed-culture fermentations, selection pressures are needed to favor AF and halt methanogenesis. Inoculum pre-treatment was studied here as elective pressure for AF demineralized cheese whey in batch processes. Alkaline (NaOH, pH 8.0, 6 h) and thermal (90 °C for 5 min, ice-bath until 23 °C) pre-treatments, were tested together with batch operations run at initial pH 7.0 and 9.0, food-to-microorganism (F/M) ratios of 0.5 to 4.0 g COD g-1VS, and under pressurized and non-pressurized headspace, in experiments duplicated in two institutes. Acetic acid was highly produced (1.36 and 1.40 g CODAcOH L-1) at the expense of methanogenesis by combining a thermal pre-treatment of inoculum with a non-pressurized batch operation started at pH 9.0. Microbial communities comprised of VFAs and alcohol producers, such asClostridium,Fonticella, andIntestinimonas, and fermenters such asLongilineaandLeptolinea. Communities also presented the lipid-accumulating and bulk and foamingCandidatus Microthrixand the metanogenicMethanosaetaregardless of no methane production. An F/M ratio of 0.5 g COD g-1VS led to the best VFA production of 1,769.38 mg L-1. Overall, inoculum thermal pre-treatment, initial pH 9.0, and non-pressurized headspace acted as a selective pressure for halting methanogen and producing VFAs, valorizing cheese whey via batch acidogenic fermentation.

O descarte de soro de queijo em corpos hídricos contribui com o processo de eutrofização. O objetivo deste trabalho é o isolamento de microalgas para cultivo em soro de queijo e pH alcalino para processos de digestão anaeróbia.

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