Metabolic changes of Neurospora crassa in the presence of oleic acid for promoting lycopene production.

Neurospora crassa has been generally recognized as a safe organism and possesses a remarkable ability to produce yellow-to-orange carotenoids. The present work mainly explored the potential mechanism of exogenous oleic acid on promoting lycopene production in N. crassa. Carbon flux was conducively channelized into the mevalonate metabolic pathway to synthesize more lycopene, associating with the increased levels of acetyl-CoA, NADPH and factors related to the mevalonate pathway. Additionally, exogenous oleic acid boosted the intracellular triacylglycerol production through de novo and ex novo fatty acid synthesis pathways, which contributed to improving the accumulation of lycopene via lipid bodies. Further, the regulated fatty acid profile also enhanced the storage capacity of lipid bodies. Consequently, this study provided an effective strategy to enhance the lycopene production in N. crassa by adding oleic acid to the culture medium and elucidated an extraordinary insight into the potential mechanism.

Changes in cell membrane properties and phospholipid fatty acids of bacillus subtilis induced by polyphenolic extract of Sanguisorba officinalis L.

Sanguisorba officinalis L. (family Rosaceae, subfamily Rosoideae) is a plant found throughout Southern Europe, Northern Africa, and Eastern Asia. This study demonstrated the antibacterial activity of a purified polyphenolic extract (PPE) from S. officinalis L. against Bacillus subtilis using growth inhibitory and apoptosis assays, and investigated the antibacterial mechanism responsible for changes in cell membrane properties. Fourier transform infrared spectroscopy suggested that PPE altered the cell wall and membrane properties of B. subtilis. Further determination of cell membrane integrity and permeability revealed that B. subtilis membrane integrity was more severely damaged by PPE at the minimum inhibitory concentration (MIC) than at the minimum bactericidal concentrati on (MBC). Instead, PPE at the MBC reduced cell membrane fluidity by significantly decreasing the proportion of anteiso- and iso-branched phospholipid fatty acids (PLFAs) from 64.17 ± 0.28% and 27.23 ± 0.03% in the control to 5.57 ± 1.06% and 6.00 ± 1.40%, respectively (P < 0.001). Scanning electron microscopy revealed different effects of PPE on cell morphology, demonstrating that, at the MIC and MBC, PPE exerted antibacterial activity by disrupting the cell membrane and reducing cell membrane fluidity, respectively. Consequently, this study elucidated changes in the bacterial membrane due to exposure to PPE and its potential use as an antimicrobial agent. PRACTICAL APPLICATION: The abuse of synthetic chemical preservatives raises food safety concerns; however, plant-derived polyphenolic compounds may be a safe and effective alternative. This study demonstrated the strong antibacterial activity of a purified polyphenolic extract (PPE) of Sanguisorba officinalis L. and revealed its antibacterial mechanism against Bacillus subtilis, suggesting that it may provide a useful antimicrobial agent in food industry applications.