Production and characterization of a thermostable antifungal chitinase secreted by the filamentous fungus Aspergillus niveus under submerged fermentation

Abstract

The filamentous fungus produced extracellular antifungal chitinase when cultured under submerged fermentation (SbmF) using crab shells as the carbon source. Maximal chitinase production was achieved at 192 h of cultivation using minimal medium containing 1% chitin. The enzyme was purified 1.97-fold with 40% recovery by ammonium sulfate precipitation and Sephadex G-100 gel filtration. The molecular mass was estimated to be 44 kDa by both 12% SDS-PAGE and Sepharose CL-6B gel filtration. Maximal chitinase activity was obtained at 65 °C and pH 5.0. The enzyme was fully stable at 60 °C for up to 120 min and the enzymatic activity was increased by Mn. In the presence of reducing and denaturing compounds, the enzyme activity was not drastically affected. The chitinase was able to hydrolyze colloidal chitin, azure chitin, and 4-nitrophenyl -acetyl-β-D glucosaminide; for the latter, the and maximal velocity () were 3.51 mM and 9.68 U/mg of protein, respectively. The chitinase presented antifungal activity against (MIC = 84 µg/mL), (MIC = 21 µg/mL), (MIC = 24 µg/mL), (MIC = 24 µg/mL), and (MIC = 21 µg/mL). The fungus was able to produce a thermostable and denaturation-resistant chitinase able to inhibit fungal development, signaling its biotechnological potential.

Current Perspectives on Chitinolytic Enzymes and Their Agro-Industrial Applications

“…SmF is the most widely used method for chitinase production from different microbes, such as Streptomyces pratensis strain KLSL55 [ 74 ], Trichoderma viride [ 75 ], Aspergillus niveus [ 76 ], Beauveria bassiana [ 77 ], and Bacillus cereus GS02 [ 78 ]. The fermentation may be operated in batch, fed-batch, or continuous mode, depending on the type of substrate and microorganism being used.…”

Production of Thermophilic Chitinase by Paenibacillus sp. TKU052 by Bioprocessing of Chitinous Fishery Wastes and Its Application in N-acetyl-D-glucosamine Production

“…Interestingly, in the presence of 2-ME, the activity of Paenibacillus sp. TKU052 chitinase significantly increased to 129.70% of its initial activity, demonstrating that cysteine residues are not involved in the formation of its catalytic center [ 52 ]. Earlier studies have reported strong inhibition of several chitinases by 2-ME, such as ChiA-Pt70 from P. timonensis LK-DZ15 [ 38 ] and CHI from P. chitinolyticus UMBR 0002 [ 1 ].…”

Aspergillus spp. eliminate Sclerotinia sclerotiorum by imbalancing the ambient oxalic acid concentration and parasitizing its sclerotia

“…The DHN melanin of S. sclerotiorum can survive boiling concentrated nitric and sulfuric acids, and boiling saturated NaOH (Butler et al ., 2009). On the other hand, the optimal pH for the highest activity of chitinase from Aspergillus ran between 5 and 6.5 (Brzezinska and Jankiewicz, 2012; Alves et al ., 2018), while the ambient pH surrounding sclerotia is acidic due to the high content of oxalic acid in sclerotial exudates (Xing et al ., 2015). Therefore, high melanin content in the rind layer and acidic ambient pH are natural obstacles for Aspergillus chitinase and beta‐1,3‐glucanase enzymes, which supports our finding that sclerotia remain intact and solid.…”