Iron as a multifunctional factor in aspergillus niger mya 135: fungal morphology, lipase production and lipase enhancer

SALVATIERRA HN; VAZQUEZ SC; BAIGORI M; PERA L

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress; 2019

 Filamentousfungi have been broadly used in biotechnological processes as cell factoriesdue to their metabolic versatility. They are able to secrete high levels ofenzymes, antibiotics, vitamins, polysaccharides and organic acids. However, oneparticular obstacle with this kind of microorganisms focuses on theirmorphological form. They can show linear filaments to highly branchedstructures, and in submerged culture growth morphologies varying from compactpellets to dispersed mycelia. In turn, several fungal processes can be directlyor indirectly affected. Those growth morphological patterns are generallyinduced by extracellular factors and accomplished by genetic and biochemicalfactors. In this connection, we previously reported that FeCl decreasesthe mycelium-bound ß-N-Acetyl-D-glucosaminidase activity (a relative marker ofthe wall lytic potential) from Aspergillus niger ATCC MYA 135 and yieldsa dispersed mycelium in its presence. Here, both the fungal morphology and thelipase activity obtaining in the presence of an optimized culture mediumsupplemented with FeCl 3 wereanalyzed. The role of this salt as lipase enhancer was assessed as well.Firstly, the extracellular lipase production was conducted in an orbital shakerat 30 °C during 192 h by using a mineral medium supplemented with 1 g/l FeCl 3 anda final conidial concentration of about 10 3 5 conidiaper ml. After 24 h of fermentation, 2 % (v/v) of olive oil was added asinducer. Thus, the highest specific activity (15.51 ± 0.78 U/mg) was obtainedat 96 h of cultivation. This activity value was 10 fold compared with its controlwithout FeCl supplementation.Secondly, a new fermentation of 96 h was conducted. The mycelium was examinedby scanning electron microscopy displaying clumps structures with scarceramified hyphae. The supernatant, collected by filtration, was also evaluatedas biocatalyst in hydrolytic and synthetic reactions as follow. The role ofiron as lipase enhancer was studied in native PAGE by using 1.3 mM ofa-naphthyl acetate as substrate. Released naphthol was bound with 1 mM FastBlue to give a colored product. Preincubation of lipase bands during 30 min inthe presence of 0.1 g/l FeCl 3 resultedin a significant increase of the activity signal. Additionally, theextracellular lipase activity was immobilized in silica gel by adsorption. Theelemental analysis performed under SEM-EDX (Energy-dispersive X-rayspectroscopy) evidenced the presence of iron. This biocatalyst was assayed toproduce biodiesel compounds in a solvent-free system using soybean oil andbutanol (1:4) as substrates. After a three-stepwise addition of butanol, abiodiesel conversion of 93.36 % was reached. Therefore, it can be concludedthat FeCl 3 3 actedby altering fungal morphology, increasing lipase production and improving theperformance of enzymatic activity. This research was supported by the followingfunding sources: FONCYT (PICT 20152596) CONICET (P-UE 2016-0012) and UNT (PIUNTD606).