Mycosubtilin belongs to the family of lipopeptides. Different isoforms with various antifungal activities can be obtained according to the length and the isomery of the fatty acid. In this work, the activities of the mycosubtilin isoforms were first studied against the pathogen Aspergillus niger, revealing the high activity of the anteiso-C17 isoform. Modification of the mycosubtilin isoform patterns during cultures of the natural strain Bacillus subtilis ATCC 6633 was then investigated through amino acid feeding experiments. In parallel, single-gene knockouts and single-gene overexpression, leading to the overproduction of the anteiso-C15 fatty acid chains, were predicted using informatics tools which provide logical reasoning with formal models of reaction networks. In this way, it was in silico predicted that the single overexpression of the ilvA gene as well as the single knockout of the codY gene may lead to the overproduction of anteiso-C15 fatty acid chains. For the first time, it has been demonstrated that overexpression of ilvA helps to enhance the furniture of odd anteiso fatty acids leading to a favored mycosubtilin anteiso-C17 production pattern (+41%). Alternatively, a knock-out codY mutant led to a higher furniture of even iso fatty acids, leading to a favored mycosubtilin iso-C16 production pattern (+180%). These results showed that increased selective synthesis of particular isoforms of mycosubtilin through metabolic engineering is feasible, disclosing the interest of these approaches for future development of lipopeptide-producing strains.

Post–Weaning Multisystemic Wasting Syndrome (PMWS) can result in mortality levels of up to 80% in weaned piglets, and Porcine Circovirus type 2 (PCV2) has been identified as one of the primary causative agents. Neutraceutical products, based on plant and herbal extracts and containing high levels of natural antioxidants may be beneficial in reducing stress on the piglets’ immune system by elevating blood antioxidant levels, and assisting with the piglets defence against PMWS. The aim of this experiment was to assess the effect of supplementation with neutraceutical products on the growth performance and antioxidant activity in liver and plasma of piglets. It was undertaken on a farm positive for PCV2, but where pigs were not showing clinical signs of PMWS. Groups of newly weaned pigs were offered one of three diets ad libitum for a period of 26 days, standard creep and starter/link control rations, or one of two experimental rations (including Neutraceutical–mix, N, or Lycopene, L), chosen for their potential to boost antioxidant activity. Growth performance and feed intake were monitored, and samples of blood and liver collected at slaughter (54 days of age) and analysed for antioxidant activity. Although L pigs ate significantly less feed during the creep period (P<0.05), there were relatively few performance differences between treatments. However total antioxidant activity in liver samples was significantly higher for the N treatment (P<0.001) and activity of plasma superoxide dismutase was significantly higher in the L group. In conclusion, growth performance of weaned piglets following the addition of Neutraceutical supplements was similar to control groups, and there were significant increases in antioxidant activity of these animals. On the basis that increased levels of circulating blood antioxidants reduce stress on the piglets’ immune system, the results of the current study suggest that these supplements may be of benefit to piglets under immune stress, such as in clinical cases of PMWS.

No abstract