Construction of Streptomyces coelicolor A3(2) mutants that exclusively produce NA4/NA6 intermediates of agarose metabolism through mutation induction.

NA4/NA6, an intermediate degradation product of ß-agarase, is a high value-added product with anticancer, anti-obesity, and anti-diabetic effects. Therefore, a method that enables the efficient production of NA4/NA6 would be useful from economic and medical perspectives. In this study, we aimed to generate a Streptomyces coelicolor A3(2) mutant M22-2C43 that produces NA4/NA6 as a final product; this method serves as a more efficient alternative to the enzymatic conversion of ß-agarase for the generation of these products. The M22-2C43 strain was generated through two rounds of mutagenesis and screening for increased ß-agarase activity and effective production of NA4/NA6. We assembled the complete genomes of two mutants, M22 and M22-2C43, which were identified following a two-round screening. Large and small genetic changes were found in these two mutants, including the loss of two plasmids present in wild-type S. coelicolor A3(2) and chromosome circularization of mutant M22-2C43. These findings suggest that mutant M22-2C43 can produce NA4/NA6 as a degradation product due to functional inactivation of the dagB gene through a point mutation (G474A), ultimately preventing further degradation of NA4/NA6 to NA2. To our knowledge, this is the first report of a microbial strain that can effectively produce NA4/NA6 as the main degradation product of ß-agarase, opening the door for the use of this species for the large-scale production of this valuable product.

Anti-obesity effect of Neoagaro-oligosaccharides with overweight and obese subjects: a 16-week, randomized, double-blind, placebo-controlled clinical trial.

BACKGROUND: This trial aimed to evaluate the anti-obesity effects and safety of Neoagaro-oligosaccharides (NAOs) in humans in a 16 week, randomized, double-blind, placebo-controlled clinical trial. METHODS: One hundred overweight or obese subjects with a body mass index of 23 to 34.9 kg/m2 and a percent body fat of > 25% for males or > 30% for females were enrolled. NAOs or placebo products were administered at 3 g (twice a day, four capsules once) each for 16 weeks. Efficacy and safety biomarkers were measured before and after intervention. RESULTS: After 16 weeks of intervention, the group administered with NAOs had statistically significant decreases in visceral fat area and visceral-subcutaneous fat area ratio compared to the placebo group. The NAOs group suppressed the increase in weight and BMI compared to the placebo group, which was significant between groups. High-density lipoprotein- cholesterol was increased in the group administered with NAOs, which showed a significant trend compared to the placebo group. Clinical changes were not observed for any safety biomarkers. CONCLUSIONS: These results suggest that NAOs have a beneficial effect on obesity. Thus, NAOs could be used as an anti-obesity supplement without side effects. TRIAL REGISTRATION: cris.nih.go.kr: (KCT0006640, 07/10/2021).