Pilot-scale production and liquid formulation of Rhodotorula minuta, a potential biocontrol agent of mango anthracnose

Abstract

Aims: To develop a pilot-plant fermentation process for the production of the yeast Rhodotorula minuta, to be used as a biocontrol agent of mango anthracnose, using a low-cost culture medium. To develop a stable liquid formulation that preserve high viability of the yeast stored at 4°C. Methods and Results: Keeping constant the volumetric power input, a fermentation process was scaled-up from shake flasks to a 100 l bioreactor. Preharvest applications of the yeast resulted in postharvest anthracnose severity equal or lower than that observed with a chemical fungicide. Glycerol was added to the formulation as water activity reducer and xanthan gum as a viscosity-enhancing agent. Yeast initial concentration of 10 10 CFU mlresulted in 4-5 orders of magnitude decrease after 1 month of storage at 4°C, whereas when it was formulated at 10 9 CFU ml )1 , the decrease was of two orders of magnitude in 6 months. Conclusions:The fermentation process was successfully scaled-up using a low-cost culture medium. Postharvest anthracnose severity could be considerably reduced using this yeast. Formulating the yeast at 10 9 CFU ml )1and adding glycerol (20%) and xanthan (5 g l )1 ) avoided both contamination and yeast sedimentation and it was able to preserve up to 10 7 CFU ml )1 after 6 months at 4°C.Significance and Impact of the Study: The yeast R. minuta is reported as a novel antagonistic micro-organism against the pathogen Colletotrichum gloeosporioides. Pilot plant production of this yeast allowed us to conduct field tests in commercial orchards during three harvest seasons. Yeast suspensions applied to mango trees reduced the fruit anthracnose severity in levels similar or better than chemical fungicides.

Responses of Yeast Biocontrol Agents to Environmental Stress

“…Results indicated that a shelf life of approximately 7 months could be obtained without a significant loss in viability or efficacy when C. sake cells were grown in a sorbitol-modified medium and then stored in an isotonic solution of trehalose. In another pilot-scale study, production of a liquid formulation of Rhodotorula minuta was evaluated (77). The yeast was formulated at 10 9 CFU/ml in a phosphate buffer solution, with the addition of glycerol (20%) and xanthan (0.5%).…”

Screening of iron-enriched fungus from natural environment and evaluation of organically bound iron bioavailability in rats

“…Almost all of the Rhodotorula are non-toxic (Patiño-Vera et al, 2005;Arras et al, 1999). In the present study, the acute oral toxicity test was verified, and Rhodotorula No.BY1109 was safe (Data not shown).…”

The science, development, and commercialization of postharvest biocontrol products

“…Isotonic, liquid formulations of C. sake CPA-1 have been reported to be a suitable alternative to solid formulations (Abadias et al, 2003b;Torres et al, 2003). Liquid formulations have also been tested with R. minuta (Patiño-Vera et al, 2005), C. laurentii (Liu et al, 2009), and P. anomala (Melin et al, 2011).…”

“…In general, liquid-phase cultures are used for bacteria and yeasts and solid-phase cultures are used for most fungi. Optimized mass production systems have been described for some postharvest biocontrol agents, including bacteria such as P. agglomerans CPA-2 (Costa et al, 2001), P. agglomerans PBC-1 (Manso et al, 2010) and B. subtilis CPA-8 (Yánez-Mendizábal et al, 2012b), yeasts such as C. sake CPA-1 (Abadias et al, 2003a,b), A. pullulans (Mounir et al, 2007), and Rhodotorula minuta (Patiño-Vera et al, 2005), and fungi such as Penicillium frequentans 909 (De Cal et al, 2002), and Epicoccum nigrum (Larena et al, 2004).…”