Physiological and biochemical changes induced by osmolality in halotolerant aspergilli

Aspergillus ventii and Aspergillus parasiticus halotolerant and alkali-resistant fungi were isolated from hypersaline soil of Wadi El-Natroun, Egypt by using a complex medium of high salt concentration (20% NaCl [w/v]). They were able to grow and resist the salt stress to about 20-25% NaCl and the alkaline condition tentatively to pH about 10.5. The presence of high salt concentration distorts the sporogenesis and stunt the conidiophores as well as inhibits the antimicrobial agent(s) and some extracellular hydrolytic enzymes (lipase(s) and amylase(s)). The application of some exogenous compatible solutes particularly trehalose, alpha-ketoglutarate and glycerol improves the growth and increases the resistance to salt stress (osmolality) of the two fungal isolates to about 27.5-29% NaCl (w/v). Results of the biochemical analysis (total soluble proteins, carbohydrates and lipids) PAGE and TLC of amino acid analysis support the suggestion that each species of Aspergillus has a specific mechanism for adaptation.