Gram-positive bacteria lactate production

Another highly potential production species is the gram-positive bacteria Clostridium propionicum. This microorganism is able to utilise lactate, glycerol and alanine as substrate. Propionate, acetate, formate, n-propanol and succinate are produced. The optimal pH value is 6.8 and the best temperature is 30 °C. C. propionicum uses the acrylic acid pathway to produce the desired product... 

This chapter describes dental caries (tooth decay) and its causes. Sucrose and other mono- and disaccharides are metabolized to acid (lactate) by bacteria that remain in stagnation areas of the teeth. Rats and hamsters fed a 50% sucrose diet developed a caries-sensitive, predominantly gram-positive microbiota that became caries resistant when the rodents were fed penicillin (Sect. 1). Further studies identified Streptococcus mutans (S. mutans) as the etiological agent. This organism synthesizes an insoluble polysaccharide capsule that is stable and retains lactate at the enamel surface (Sect. 2). The key enzyme, glucosyl transferase, is related to salivary amylase which adheres to oral bacteria and enhances bacterial acid production. The chapter concludes with a discussion of salivary and other factors responsible for the marked variation observed in individual caries experience (Sect. 3). 

This unusual form of lactic acidosis is due to increased production and accumulation of D-lactate in circulation. The normal isomer synthesized in the human body is L-lactate but the D-lactate isomer can occur in patients with jejunoileal bypass, small bowel resection, or other types of short bowel syndrome. In these patients, ingested starch and glucose bypass the normal metabolism in the small intestine and lead to increased delivery of nutrients to the colon where gram-positive, anaerobic bacteria (e.g., Lactobacilli) ferment glucose to D-lactate. The D-lactate is absorbed via the portal circulation. 

Various bacteria own the ability to produce propionic acid within their metabolic pathways. Present-day research is focused on strains of Propionibacteriaceae and Clostridiaceae. Propionibacteria are using the dicarboxylic acid pathway (methylmalonyl coenzyme A-pathway) to produce the desired product. These gram-positive, anaerobic bacteria are able to use glucose, sucrose, lactate, lactose and glycerol as carbon source. The metabolic end products are propionate, succinate, carbon dioxide and acetate. Professionals acknowledge Propionibacterium... 

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