Structural basis for the cold activation and adaptation of anα-agarase from marine bacterium Catenovulum agarivorans STB13

Enzymes have high activity at low temperatures are defined as cold-adapted enzymes,but few enzymes show an activation effect after low-temperature incubation.In this study,we cloned an agarase from the marine bacte-rium Catenovulum agarivorans STB13(Ca-AGA)and expressed the protein in Bacillus subtilis.The enzyme exhibited a peculiar cold activation,which was enhanced by 5-fold after incubation at-20℃ or 4℃ for 6 h.Fluorescence and CD spectra studies confirmed the secondary and tertiary structural changes in Ca-AGA at low temperature,which formed compact protein structures after low-temperature treatment.The enzyme also showed outstanding cold adaptation,retaining approximately 60%of its maximum activity at 10℃.Based on a bioinformatics analysis,the carbohydrate-binding modules(CBMs)and long linker region were presumed to play a crucial role in cold adaptation due to a relatively high percentage of acidic residues and a negative charge density compared to the catalytic domain.A mutation that truncated the linker-CBM region resulted in a 59.97%reduction of the activity at 10℃.This study describes anα-agarase of cold activation and adaptation in detail,which may have great potential for producing functional agaro-oligosaccharides in food and pharmaceutical industrial applications at ambient temperature.

Chinese agricultural technology transfer to African typical dry areas:practice and experience

Africa has experienced increasing aridity and higher frequency of droughts due to climate change during the half past century with possible adverse effects on agricultural production,especially in dry areas with low rainfall.Under the auspices of the Africa Water Action Program between the Chinese Ministry of Science and Technology(MOST)and the United Nations Environment Program(UNEP),the Institute of Agricultural Environment and Resources,Shanxi Academy of Agricultural Sciences(SAAS-IAER)worked closely with domestic and overseas partners on technology transfer in Morocco,Zambia,Egypt,Niger and Ethiopia from 2008 to 2013.A drought early warning system has been established and validated,and drought adaptation technologies have been trialed,modified,demonstrated and extended in African countries,and this shows great potential to increase crop production,water and fertilizer use efficiency and desert control in rainfed areas of Africa.The project has continued for six years and is a successful case of technology transfer and capacity building in Africa.The knowledge and experience gained will be useful to researchers,technicians,aid agencies and policy makers who work on agricultural technology transfer for in dry areas of Africa.