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

Abstract

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 byCl. 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.

Stable coexistence of two Caldicellulosiruptor species in a de novo constructed hydrogen-producing co-culture

“…This approach has been widely adapted in food fermentations [5,6] and successfully employed for lab-scale bioethanol [7-9], acetic acid [10] and lactic acid [11] production. It also provides an essential tool for fundamental studies on the different mechanisms of microbial interactions [12-16].…”

Hydrogen production by Clostridium thermolacticum during continuous fermentation of lactose

“…We observed and quantiÿed production of hydrogen as a by-product in batch [7] and continuous culture. The objective of the present study was to assess the amount of hydrogen formed during lactose fermentation in continuous culture.…”

Nutritional stress induces exchange of cell material and energetic coupling between bacterial species

“…Many studies have examined the syntrophic growth of sulfate-reducing bacteria (SRB) acting like secondary fermenters and methanogenic archaea [9][10][11] . Most recently, the metabolic interaction between Clostridia, acting as primary fermenters, and methanogenic archaea has also been studied 12,13 , highlighting a symbiotic process of interspecies hydrogen transfer that does not require physical interaction. However, very few studies have examined interaction between SRB and Clostridia, and little is known about the complex interactions that occur in natural bacterial consortia and how primary fermenter bacteria such as Clostridia compete with other anaerobes like SRB 8 .…”