Statistical optimization of kojic acid production by a UV-induced mutant strain of Aspergillus terreus

ABSTRACT The ability of four Aspergillus strains for biosynthesis of kojic acid was evaluated among which Aspergillus terreus represented the highest level (2.21 g/L) of kojic acid production. Improvement kojic acid production ability of A. terreus by random mutagenesis using different exposure time to ultraviolet light (5-40 min) was then performed to obtain a suitable mutant of kojic acid production (designated as C5-10, 7.63 g/L). Thereafter, design of experiment protocol was employed to find medium components (glucose, yeast extract, KH2PO4 (NH4)2SO4, and pH) influences on kojic acid production by the C5-10 mutant. A 25-1 fractional factorial design augmented to central composite design showed that glucose, yeast extract, and KH2PO4 were the most considerable factors within the tested levels (p < 0.05). The optimum medium composition for the kojic acid production by the C5-10 mutant was found to be glucose, 98.4 g/L; yeast extract, 1.0 g/L; and KH2PO4, 10.3 mM which was theoretically able to produce 120.2 g/L of kojic acid based on the obtained response surface model for medium optimization. Using these medium compositions an experimental maximum Kojic acid production (109.0 ± 10 g/L) was acquired which verified the efficiency of the applied method.

Enhancement of botrallin and TMC-264 production in liquid culture of endophytic fungus Hyalodendriella sp. Ponipodef12 after treatments with metal ions

Background: Hyalodendriella sp. Ponipodef12, an endophytic fungus from a poplar hybrid, was a high producer of botrallin and TMC-264 with various bioactivities. In this study, the influences of eight metal ions (i.e.,Mn2+,Na+, Mg2+,Zn2+,Cu2+,Fe2+,Fe3+ and Al3+) on botrallin and TMC-264 production in liquid culture of the endophytic fungus Hyalodendriella sp. Ponipodef12 were investigated. Results: Three most effective metal ions (Zn2+,Cu2+ and Mg2+) along with their optimum concentrations were screened. The optimum addition time and concentrations of Zn2+,Cu2+ and Mg2+ were further obtained respectively for improving botrallin and TMC-264 production. The combination effects of Zn2+,Cu2+ and Mg2+ on the production of botrallin and TMC-264 by employing statistical method based on the central composite design (CCD) and response surface methodology (RSM) were evaluated, and two quadratic predictive models were developed for botrallin and TMC-264 production. The yields of botrallin and TMC-264, which were predicted as 144.12 mg/L and 36.04 mg/L respectively, were validated to be 146.51 mg/L and 36.63 mg/L accordingly with the optimum concentrations of Zn2+ at 0.81 mmol/L, Cu2+ at 0.20 mmol/L, and Mg2+ at 0.13 mmol/L in medium. Conclusion: The results indicated that the enhancement of botrallin and TMC-264 accumulation in liquid culture of the endophytic fungus Hyalodendriella sp. Ponipodef12 by the metal ions and their combination should be an effective strategy.

Characterization and evaluation of coconut aroma produced by Trichoderma viride EMCC-107 in solid state fermentation on sugarcane bagasse

Background Sugarcane bagasse was shown to be an adequate substrate for the growth and aroma production by Trichoderma species. In the present work the ability of Trichoderma viride EMCC-107 to produce high yield of coconut aroma in solid state fermentation (SSF) by using sugarcane bagasse as solid substrate was evaluated. The produced aroma was characterized. Results Total carbohydrates comprised the highest content (43.9% w/w) compared with the other constituents in sugarcane bagasse. The sensory and gas chromatography-mass spectrometric (GC-MS) analysis revealed that the highest odor intensity and maximum yield of volatiles were perceived at the 5th d of induction period. The unsaturated lactone, 6-pentyl-α-pyrone (6-PP), was the major identified volatile compound. Saturated lactones, δ-octalactone, γ-nonalactone, γ-undecalactone, γ-dodecalactone and δ-dodecalactone, were also identified in the coconut aroma produced during the induction period (12 d). A quite correlation was found between the composition and odor profile of the produced aroma. The effect of varying the concentration of sugarcane bagasse on 6-PP production and biomass growth was evaluated. The results revealed high 6-PP production at 4.5 g sugarcane bagasse whereas the biomass showed significant (P < 0.05) increase by increasing the concentration of sugarcane bagasse. Conclusion The concentration of 6-PP, the most contribution of coconut aroma, produced in present study (3.62 mg/g DM) was higher than that reported in previous studies conducted under the same fermentation conditions. The significant increase in biomass with increasing the concentration of sugarcane bagasse may be attributed to the increase in sugar content that acts as carbon and energy source.