Solid-state fermentation-supported enhanced production of α-galactosidase by a deoxyglucose-resistant mutant of Aspergillus niger and thermostabilization of the production process

Abstract

The aim of the present investigation was to comparatively evaluate the behaviour of A. niger and its derepressed mutant in production of a-galactosidase in submerged (SmF) and solid state fermentation (SSF) using basal Vogel's medium or corn steep liquor as nitrogen source and observe the response of latter source under both cultural techniques under different temperature regimes, and determine if SSF can be exploited in a wide range of temperature expected to vary in this fermentation system. All studies were performed in both systems under preoptimized cultural conditions. Higher melting temperature and negative values of entropy of activation in SSF indicated that the genetic system of both organisms was thermodynamically resistant in the presence of corn steep liquor but sensitive to inactivation in the presence of Vogel's nitrogen sources in submerged fermentation. This was reflected as the organisms demanded higher magnitudes of energy for product formation in the presence of ammonium salts. Studies on influence of corn steep liquor revealed that it had stabilizing effect too in both fermentation systems but the mutant strain was more stable in both fermentation systems. Because of these properties, the mutant organism may be exploited for bulk production of a-galactosidase in SSF under condition where temperature may fluctuate during fermentation.

Kinetics and thermodynamics of high level β-glucosidase production by mutant derivative of Aspergillus niger under submerged growth conditions

“…Awan et al (2009) has also reported change in enthalpy (21.6 and 19.1 kJ/mol) and entropy (-134.3 and -138.4 J/mol/K) of parent and mutant A. niger, respectively for αgalactosidase production in solid state fermentation using wheat bran supplemented with glucose as carbon source and corn steep liquor as a nitrogen source. Low magnitudes of activation energy, enthalpy, Gibbs free energy and entropy for product formation are considered to be indices for thermostability of metabolic pathway (Rajoka et al, 2009). Therefore, we suggest that the mutation had significant effect in thermostabilization of the metabolic network of mutant (M6) during BGL production, which might be due to either formation of chaperons or hyperglycosylation of enzymes of the production metabolic network as reported earlier (Aiba et al, 1973).…”

“…The ΔS* (x) and ΔS* (p) for cell mass and BGL production were also determined. The thermodynamic growth parameters in submerged fermentation of the mutant were even lower than reported for thermotolerant Kluveromyces marxianus, Humicola lanuginosa (Bokhari et al, 2008) and A. niger NIAB 280 (Rajoka et al, 2009). Awan et al (2009) has also reported change in enthalpy (21.6 and 19.1 kJ/mol) and entropy (-134.3 and -138.4 J/mol/K) of parent and mutant A. niger, respectively for αgalactosidase production in solid state fermentation using wheat bran supplemented with glucose as carbon source and corn steep liquor as a nitrogen source.…”

“…of Humicola lanuginose wild and mutant cells, respectively (Bokhari et al, 2008) as well as other mesophilic organisms (138.9-177 kJ/mol). The reported values in the current study were even lower than (152 and 91 kJ/mol for parent and mutant cells, respectively) of A. niger NIAB 280 for α-galactosidase production (Rajoka et al, 2009). The temperature quotient (Q 10 factor) for cell mass formation and BGL production by both strains was also calculated and presented in Table 3.…”

Micropropagule production from Trichoderma harzianum EGE-K38 using solid-state fermentation and a comparative study for drying methods

“…For micropropagule production, 40 g of zeolite moisturized by distilled water containing Vogel's salts (26)(27)(28) was used. Investigations of glucose concentration as a carbon source and supplementation of the production medium with various nitrogen sources including yeast extract, soybean flour, peptone, corn steep solids (CSS), and inoculation were performed by exactly the same procedure as described for the natural substrates.…”