To achieve higher antibiotic streptolydigin productivity through metabolic regulation, propionate was fed during the fermentation of Streptomyces lydicus AS 4.2501. The effects of propionate feeding on streptolydigin ...To achieve higher antibiotic streptolydigin productivity through metabolic regulation, propionate was fed during the fermentation of Streptomyces lydicus AS 4.2501. The effects of propionate feeding on streptolydigin production and intracellular fluxes were investigated. The highest streptolydigin production yield of 95.10mg·L-1 was obtained when 2mmol·L-1 of sodium propionate was added at 60h of cultivation into shake-flask culture. This yield is 23.06% higher when compared to that of a batch culture without propionate supplementation. It was also found that when propionate was added, much more organic acids were excreted. Metabolic flux analysis was per-formed and it demonstrated that the carbon fluxes of the pentose phosphate pathway and the anaplerotic reaction were significantly increased after propionate feeding. The carbon flux from pyruvate to acetyl-CoA was determined to be 24.7, which was 12.27% higher than that in the batch culture. This study indicated that the glu-cose-6-phosphate and pyruvate nodes were potential bottlenecks for increasing streptolydigin productivity. Potential targets and strategies that could be manipulated through genetic and process engineering to increase the production of streptolydigin were also suggested.展开更多
Possible ways to reduce antibiotic use in rabbit production are discussed, based on a literature survey. Several management strategies have been proven to successfully reduce disease pressure in rabbit production. The...Possible ways to reduce antibiotic use in rabbit production are discussed, based on a literature survey. Several management strategies have been proven to successfully reduce disease pressure in rabbit production. The primary way of reducing risk of disease is ＂all-in all-out＂ management, as it allows thorough cleaning and disinfection. A second tool is choosing reproduction stock with a minimal disease level. Animals with a near Specific-Pathogen-Free （SPF） status, or even entirely disease-free animals, lead to high-health-status farms where antibiotics are rarely used. To reduce the risk of enteritis, quantitative aspects in the early fattening stage are important, apart from some ,qualitative feed characteristics （especially the carbohydrate complex）. Finally, despite discussions about their effectiveness, pro/prebiotics and some other additives have shown some potential in reducing enteric problems. Alternatives to antibiotics are only useful, however, if the whole chain （reproduction stock producers, breeders, feed companies, slaughterhouses and even veterinarians） is convinced and forced into a globally consistent strategy. In the absence of such a consistent approach, both preventive and curative use of antibiotics remains the easiest and most inexpensive way to control disease in rabbit production.展开更多
基金Supported by the National Natural Science Foundation of China (No.20425620)the Program for Changjiang Scholars andInnovative Research Team in University from the Ministry of Education of China.
文摘To achieve higher antibiotic streptolydigin productivity through metabolic regulation, propionate was fed during the fermentation of Streptomyces lydicus AS 4.2501. The effects of propionate feeding on streptolydigin production and intracellular fluxes were investigated. The highest streptolydigin production yield of 95.10mg·L-1 was obtained when 2mmol·L-1 of sodium propionate was added at 60h of cultivation into shake-flask culture. This yield is 23.06% higher when compared to that of a batch culture without propionate supplementation. It was also found that when propionate was added, much more organic acids were excreted. Metabolic flux analysis was per-formed and it demonstrated that the carbon fluxes of the pentose phosphate pathway and the anaplerotic reaction were significantly increased after propionate feeding. The carbon flux from pyruvate to acetyl-CoA was determined to be 24.7, which was 12.27% higher than that in the batch culture. This study indicated that the glu-cose-6-phosphate and pyruvate nodes were potential bottlenecks for increasing streptolydigin productivity. Potential targets and strategies that could be manipulated through genetic and process engineering to increase the production of streptolydigin were also suggested.
文摘Possible ways to reduce antibiotic use in rabbit production are discussed, based on a literature survey. Several management strategies have been proven to successfully reduce disease pressure in rabbit production. The primary way of reducing risk of disease is ＂all-in all-out＂ management, as it allows thorough cleaning and disinfection. A second tool is choosing reproduction stock with a minimal disease level. Animals with a near Specific-Pathogen-Free （SPF） status, or even entirely disease-free animals, lead to high-health-status farms where antibiotics are rarely used. To reduce the risk of enteritis, quantitative aspects in the early fattening stage are important, apart from some ,qualitative feed characteristics （especially the carbohydrate complex）. Finally, despite discussions about their effectiveness, pro/prebiotics and some other additives have shown some potential in reducing enteric problems. Alternatives to antibiotics are only useful, however, if the whole chain （reproduction stock producers, breeders, feed companies, slaughterhouses and even veterinarians） is convinced and forced into a globally consistent strategy. In the absence of such a consistent approach, both preventive and curative use of antibiotics remains the easiest and most inexpensive way to control disease in rabbit production.
