Improving low water activity and desiccation tolerance of the biocontrol agent Pantoea agglomerans CPA-2 by osmotic treatments

Abstract

Aims: To study the improvement of tolerance to low water activity (aw) and desiccation during spray drying in Pantoea agglomerans cells subjected to mild osmotic stress during growth. Methods and Results: The micro‐organism was cultured in an unmodified liquid (control) or in aw‐modified media, and viability of these cells was evaluated on unstressed (0·995) and 0·96 aw stressed solid media, in order to check total viability and aw stress tolerance respectively. Significant improvements in viability on unmodified medium were observed with cells grown for 24 h in NaCl 0·98 aw, glycerol 0·98 aw and 0·97 aw and for 48 h in NaCl 0·98 aw and 0·97 aw modified media. Both yield improvements and water stress tolerance were achieved with low aw media. Cells grown for 24 h in NaCl 0·98 aw or for 48 h in NaCl 0·98 aw, 0·97 aw and 0·96 aw, glucose 0·97 aw and glycerol 0·97 aw showed improved aw stress tolerance in comparison with control cells. The best results were obtained with NaCl treatments (0·98 aw and 0·97 aw) which also exhibited better survival rates than control cells during spray‐drying process and maintained their efficacy against postharvest fungal pathogens in apples and oranges. Conclusions: NaCl treatments are very appropriate for improving P. agglomerans low aw tolerance obtaining high production levels and maintaining biocontrol efficacy. Significance and Impact of the Study: Improving stress tolerance of biocontrol agents could be an efficient way to obtain consistency and maintain efficacy of biological control under practical conditions.

Endospore production allows using spray-drying as a possible formulation system of the biocontrol agent Bacillus subtilis CPA-8

“…Considering that CPA-8 product was obtained without preconditioning the microorganism to drying and by using non-optimised carriers/protectants and conditions, our results are promising and have the potential to be improved in the future. Studies conducted by Teixidó et al (2006) and Cañamás et al (2008) have demonstrated that the preservation of microorganisms used as biocontrol agents can be improved by induction of desiccation tolerance using different methodologies, such as by growing the microorganisms in a w modified media or under sublethal thermal stress conditions. Bacillus-based products can also be formulated by producing heat-stressed endospores and by using inorganic and organic carriers (Chung et al 2007;Sorokulova et al 2008).…”

Biological control of postharvest diseases of fruit

“…This tolerance was attributed to the intracellular accumulation of compatible solutes glycine-betaine and ectoine. The osmoticadapted cells also demonstrated better survival during spray drying, and maintained its biocontrol activity to control green mould of citrus (Teixidó et al 2006). Previously it was explained that pre-harvest application of the antagonist could lead to an improvement in effectiveness.…”

Influence of post-harvest technologies applied during cold storage of apples in Penicillium expansum growth and patulin accumulation: A review

“…A similar procedure was carried out for the commercial use of the bacterium Pantoea agglomerans (Ewing and Fife) (strain CPA-2) as a BCA (Costa, Usall, Teixido, Delgado, & Viñas, 2002;Costa, Usall, Teixido, Garcia, & Viñas, 2000;Costa, Usall, Teixido, Torres, & Viñas, 2002;Nunes, Usall, Teixido, Fons, & Viñas, 2002;Nunes, Usall, Teixido, & Viñas, 2001;Teixido et al, 2005;Teixidó et al, 2006).…”