Improvement of acetate production from lactose by growing Clostridium thermolacticum in mixed batch culture

Aims: The objective of this study was to increase the acetate production by Clostridium thermolacticum growing on lactose, available as a renewable resource in the milk and whey permeate from the cheese industry. Methods and Results: Experiments for increased acetate productivity by thermophilic anaerobes grown on lactose were carried out in batch cultures. Lactose at concentration of 30 mmol l−1 (10 g l−1) was completely degraded by Cl. thermolacticum and growth rate was maximal. High concentrations of by‐products, ethanol, lactate, hydrogen and carbon dioxide were generated. By using an efficient hydrogenotroph, Methanothermobacter thermoautotrophicus, in a defined thermophilic anaerobic consortium (58°C) with Cl. thermolacticum and the acetogenic Moorella thermoautotrophica, the hydrogen partial pressure was dramatically lowered. As a consequence, by‐products concentrations were significantly reduced and acetate production was increased. Conclusion: Through efficient in situ hydrogen scavenging in the consortium, the metabolic pattern was modified in favour of acetate production, at the expense of reduced by‐products like ethanol. Significance and Impact of the Study: The use of this thermophilic anaerobic consortium opens new opportunities for the efficient valorization of lactose, the main waste from the cheese industry, and production of calcium–magnesium acetate, an environmentally friendly road de‐icer.