Bioemulsifier production by Aspergillus niger MYA 135: presumptive role of iron and phosphate on emulsifying ability

Abstract

Microbial emulsifiers are compounds employed in primary mechanisms for bioremediation of petroleum and other hydrocarbon pollutants from the environment. Although emulsifiers of biological origin are produced by microorganisms generally in response to growth on hydrocarbons, Aspergillus niger MYA 135 produced a bioemulsifier during fermentation in a sucrose-based culture medium at an initial pH of 5.0 and at 30°C. The production of bioemulsifiers can be strongly influenced by environmental factors. In this connection, a study of the effect of initial pH, the incubation temperature and presence of CaCl 2 or FeCl 3 in the culture medium was conducted. Emulsification index was increased by 112 and 206% at an initial pH 2.0 or in medium supplemented with FeCl 3 , respectively. On the other hand, emulsifying ability of Aspergillus niger supernatants was detected during the exponential phase, suggesting that bioemulsifiers accumulation and microbial growth would be related. Interestingly, this study suggests that iron and/or phosphate ions would play a key role in maintaining the emulsifying ability. Finally, factorial design was also employed to study the effects of the initial pH, the presence of FeCl 3 and the concentration of KH 2 PO 4 on the emulsification index.

Tailoring fungal morphology of Aspergillus niger MYA 135 by altering the hyphal morphology and the conidia adhesion capacity: biotechnological applications

“…On the contrary, the presence of FeCl 3 in a range of 0.5 - 10.0 mM impaired a NAGase purified extract activity (Pera et al 1997). Thus, as it was mentioned before, the addition of 1 g l -1 FeCl 3 to the BM encourages a scarcely branched mycelium and increases the production of both a mycelium-bound transesterification lipase activity (Colin et al 2011) and an emulsifier compound (Colin et al 2010a). Interestingly, in the same medium supplemented with 2% olive oil it was also observed that a specific extracellular hydrolytic lipase activity was increased by 6.6 fold after four days of incubation compared to the control (Colin et al 2010b).…”

“…Interestingly, when A. niger MYA 135 grew mainly as dispersed mycelia the presence of an extracellular compound, if any, was only detected with electron microscope (data not shown). In addition, the production of an emulsifier activity was significantly increased (p < 0.05) under environmental conditions that support dispersed mycelial growth (Colin et al 2010a). Similarly, Prosser and Tough (1991) reported that the addition of nonionic surfactants, e.g., Span, to shake-flask cultures of A. niger also decreases spore aggregation thus allowing for dispersed growth.…”

“…Besides, the specific citric acid production (g citric acid per g biomass dry mass) increases by 40%, while the volumetric productivity (g citric acid per l per h) and the yield (g citric acid per g initial sucrose) are doubled (Pera and Callieri 1997). On the other hand, the dispersed mycelium obtained in the presence of 1 g l -1 FeCl 3 is preferred for the production of both a bioemulsifier (Colin et al 2010a) and a mycelium-bound transesterification lipase activity (Colin et al 2011). …”

Production and partial characterization of bioemulsifier from a chromium-resistant actinobacteria

“…The production of microbial emulsifiers, also called bioemulsifiers, has increased in recent years because of their higher biodegradability and reduced toxicity compared to their synthetically produced alternatives (Colin et al, 2010). Bioemulsifiers are amphiphatic molecules secreted by (micro)organisms, which facilitate the uptake of water-insoluble substrates (Shete et al, 2006).…”

“…They are therefore commonly produced in response to microbial growth on hydrocarbons (Luna-Velasco et al, 2007;Martínez-Checa et al, 2007). However, there are also a few examples of bioemulsifier production during microbial growth on carbohydrates (Sarubbo et al, 2001;Colin et al, 2010).…”