Screening of a biological control bacterium to fight avocado diseases: From agroecosystem to bioreactor

Abstract

Abstract Avocado diseases remain to be a major constraint for the development of this agribusiness, which is largely led by Latin American countries. In this study, a collection of 667 native avocado bacterial isolates was established and screened for antagonistic activity and bioactive secondary metabolite production against two important avocado pathogens (Phytophthora cinnamomi and Colletotrichum gloeosporioides). The isolate ARP5.1 demonstrated the highest potential for in vitro control of the phytopathogens and was identified as Serratia sp. To enhance bioactive metabolite production by ARP5.1, different combinations of agitation speeds and aeration rates were evaluated on a stirred tank bioreactor. The activity of the crude extracts was tested and cell growth kinetics, oxygen and glucose consumption, and production of secondary metabolites were determined at the fermentation conditions of higher inhibitory activity. Results evidenced oxygen as critical factor for the biosynthesis of metabolites of interest. In addition, shear stress and glucose were limiting factors in metabolite production. Prodigiosin, serratamolide and haterumalide NC were identified in the extracts by Liquid Chromatography coupled to High-Resolution Mass Spectrometry. However, the presence of haterumalide NC might explain the high activity of the crude extract against P. cinnamomi. We concluded that this bacterium might be a promising candidate for the control of avocado pathogens in field and a good source of bioactive metabolites.