Glucose and lactose as cryoprotectants for fungal strains immobilised in sodium alginate: an emphasis on the conservation of the zygomycetes Rhizopus and Mucor

Abstract

This research aimed at investigating the cryoprotectant action of glucose and lactose on strains of Malassezia spp. and zygomycetes immobilised in sodium alginate. Twelve strains of Malassezia spp. (nine M. furfur, two M. globosa and one M. sympodialis) and 12 zygomycetes (five Rhizopus oryzae and seven Mucor hiemales) were immobilised in sodium alginate, within plastic beads, maintained in appropriate media containing glucose and lactose at concentrations of 9% and 23% and preserved at temperatures of -20 and -80 °C. Strain viability was evaluated from 15 to 270 days of storage, through the observation of macro-micromorphologic characteristics. The Malassezia spp. strains were only viable until 90 days of storage, whereas for zygomycetes, viable strains were observed until after 270 days of storage at -80 °C, in the media containing 23% glucose or lactose. The use of 23% glucose or lactose at -80 °C in a sodium alginate cell immobilisation system is efficient for cryopreserving zygomycetes. This research creates perspectives for the use of glucose and lactose in sodium alginate cell immobilisation systems for the preservation of fungi with low viability.

Easy Storage Strategies forSporothrixspp. Strains

“…3,7,17,18 Therefore, cryopreservation is the currently preferred technique in many culture collections because it decreases cell metabolic activity, allowing the isolates to remain stable for extended periods of time, in addition to preventing colony contamination. 9,12 On the other hand, the freezing process can irreversibly damage fungal cells, and hence, different cryoprotectants have been used to reduce cell damage. 9 In this study, the use of glycerol as a penetrating cryoprotectant associated with the nonpenetrating cryoprotectants sucrose or lactose was shown to be a valid alternative for the cryopreservation of the S. schenckii species complex, resulting in 100% recovery, even after 9 months of storage, at both -20°to -80°C.…”

“…Cryotubes containing saline were stored at 4°C, while those containing the cryoprotectants GL and GS were kept at -20°C and -80°C, for periods of 3, 6, and 9 months. 12,13 Viability of stored strains and conidium count At the end of each period, the strains were removed from storage and subcultured on potato dextrose agar medium (Difco, USA). Viability was defined as the ability to grow on potato dextrose agar, after storage, under any of the tested conditions.…”

“…9 Storage at freezing temperatures has been employed to preserve fungal viability using penetrating cryoprotectants such as glycerol and DMSO, 10,11 or nonpenetrating ones, such as glucose and lactose. [11][12][13] However, there are no published reports on the combined use of both classes of cryoprotectants for fungal preservation.…”

Correlation between the invasive fungal infection among and their blood glucose levels

“…The BGLs of patients of Group C are higher than 10.0 mmol/L. Among the critically ill ICU patients, the proportion of fungal infection is up to 50% primarily because blood osmotic pressure increases with high BGL, and this increase inhibits the phagocytic functions of neutrophils, reduces the ability of the body to resist infection, and causes abnormalities in the immune system, thereby promoting the spread of fungal infection and adding value to deep organizations [8]. Bueno [9] investigated the situation of fungal infection among ICU patients and reported that their BGLs should be monitored.…”