Construction of engineered Streptococcus zooepidemicus for the production of hyaluronic acid ligosaccharide / 生物工程学报

Hyaluronic acid (HA) is widely used in many fields, such as medicine, cosmetics and food. The bioactivity of HA depends on its molecular weight (Mw). Owing to the important physiological activities and special physiological functions, HA oligosaccharides have important application prospects in medicine fields. Streptococcus zooepidemicus has wide applications in commercial production of HA, due to its short fermentation cycle and strong production intensity. In order to efficiently synthesize HA oligosaccharides and solve the dissolved oxygen in the fermentation process, in this study, we overexpressed HA synthase (HasA) and introduced and optimized the leech hyaluronidase LHAase in Streptococcus zooepidemicus WSH-24. As a result, HA oligosaccharides were efficiently produced with improved dissolved oxygen. After 24 h, HA oligosaccharides production intensity reached to 294.2 mg/(L·h), and the concentration accumulated to 0.97 g/L in flask cultures, which was 1.82 times of the wild strain. Impressively, HA oligosaccharides were increased to 7.06 g/L in 3 L fermentor. The constructed Streptococcus zooepidemicus strain for producing HA oligosaccharides would have broad application prospects.

An outbreak of fatal hemorrhagic pneumonia caused by Streptococcus equi subsp. zooepidemicus in shelter dogs

An outbreak of fatal hemorrhagic pneumonia with 70~90% morbidity and 50% mortality occurred in an animal shelter in Yangju, Gyeonggi Province, Korea. Clinically, the affected dogs showed severe respiratory distress within 48 h after arriving in the shelter. The dead were found mainly with nasal bleeding and hematemesis. At necropsy, hemothorax and hemorrhagic pneumonia along with severe pulmonary consolidation was observed, though histopathological analysis showed mainly hemorrhagic bronchopneumonia. Lymphoid depletion was inconsistently seen in the spleen, tonsil and bronchial lymph node. Gram-positive colonies were shown in blood vessels or parenchyma of cerebrum, lung, liver, spleen, and kidney. Also, Streptococcus (S.) equi subsp. zooepidemicus was isolated from the various organs in which the bacterium was microscopically and histologically detected. In addition, approximately 0.9 Kb specific amplicon, antiphagocytic factor H binding protein, was amplified in the bacterial isolates. In this study, we reported an outbreak of canine hemorrhagic bronchopneumonia caused by S. equi subsp. zooepidemicus in an animal shelter in Yangju, Korea.

LASER MUTAGENESIS AND SELECTION OF STREPTOCOCCUS ZOOEPIDEMICUS PROTOPLASTS / 微生物学通报

Conditions about protoplast preparation and regeneration of Streptococcus zooepidemicus,which could produce hyaluronic acid, were studied , including the concentration of lysozyme, lytic time, different osmotic stabilizers and the preculture under the high osmotic pressure . As a result, the formation and regeneration rate of protoplasts could reach up to 94.6% and 18.5% respectively under the optimum conditions, before the digestion of lysozyme (50U/mL,39℃, 60 min) the strain was cultured for 2 hours in 0.6 mol/L NaCl high osmotic pressure liquid medium containing 1.2% Gly. Among different treatments of various laser power and irradiating time, He-Ne laser which acted for 300 seconds with 40mW /cm 2 caused lethality rate as high as 99.88%. Finally, a mutated strain was gained, whose production of HA is 2.21g/L, just 4.5 times as much as the original strain.