Bioreactor operated production of lipase: Castor oil hydrolysis using partially-purified lipase

481-486A highly stable lipase from Pseudomonas aeruginosa KKA-5 was produced by batch cultivation technique employing shake flask and 5 L - bioreactor. The bioreactor was run at different airflow rates. Low airflow rates (1 and 3 L/min), did not lead to effective growth and lipase production. Growth increased by about one order and lipase production increased by about 6 times, at an airflow rate of 5 L/min. Lipase production occurred during decelerated cell growth. A highly stable lipase was produced which retained its activity in the running bioreactor, even after a period of one month. This stable lipase was partially-purified using ammonium sulphate precipitation technique. Castor, oil was hydrolyzed using 300U crude and partially-purified lipase, each. Approximately 21-fold, partially-purified lipase could hydrolyze 81 % castor oil within a period of 96 hr, where as only 63% hydrolysis was obtained, in 216 hour, when crude lipase was used

Receptor-binding loops in alphacoronavirus adaptation and evolution

International audienceRNA viruses are characterized by a high mutation rate, a buffer against environmental change. Nevertheless, the means by which random mutation improves viral fitness is not well characterized. Here we report the X-ray crystal structure of the receptor-binding domain (RBD) of the human coronavirus, HCoV-229E, in complex with the ectodomain of its receptor, aminopeptidase N (APN). Three extended loops are solely responsible for receptor binding and the evolution of HCoV-229E and its close relatives is accompanied by changing loop-receptor interactions. Phylogenetic analysis shows that the natural HCoV-229E receptor-binding loop variation observed defines six RBD classes whose viruses have successively replaced each other in the human population over the past 50 years. These RBD classes differ in their affinity for APN and their ability to bind an HCoV-229E neutralizing antibody. Together, our results provide a model for alphacoronavirus adaptation and evolution based on the use of extended loops for receptor binding