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Biotechnology and Applied Biochemistry (2010) 55, (131–137) (Printed in Great Britain)
L-Ascorbate, a strong inducer of L-dopa (3,4-dihydroxy-L-phenylalanine) production from pre-grown mycelia of Aspergillus oryzae NRRL-1560
Irfana Mariam*1, Sikander Ali†, Asia Rehman* and Ikram-ul-Haq†
*Department of Chemistry, GC University Lahore, Katchehry Road, Lahore, 54600, Pakistan, and †Institute of Industrial Biotechnology (I.I.B.), GC University Lahore, Katchehry Road, Lahore, 54600, Pakistan
Key words: L-ascorbate, Aspergillus oryzae, L-dopa production, fuzzy-logic control, two-factorial design, L-tyrosine. Abbreviations used: cfu, colony-forming unit; I.I.B., Institute of Industrial Biotechnology; L-dopa, 3,4-dihydroxy-L-phenylalanine. 1To whom correspondence should be addressed (email majied.irfana@yahoo.com). The inductive effect of L-ascorbate on the microbiological production of L-dopa (3,4-dihydroxy-L-phenylalanine) from Aspergillus oryzae NRRL-1560 was investigated. All biochemical reactions were performed aerobically using mould mycelia as a source of enzyme tyrosinase and acetate buffer (pH 3.0) as an extractant. L-Tyrosine as a substrate was added at a level of 2.5 mg/ml. Maximal L-dopa production (1.876 mg/ml) was achieved when L-ascorbate (5.0 mg/ml) was added 6 min after the initiation of the biochemical reaction at 50 °C, consuming 2.144 mg/ml L-tyrosine. The performance of fuzzy-logic control of the reaction was found to be highly promising for improvement of the substrate conversion rate (~80%). After optimizing the reaction conditions, particularly the addition of L-ascorbate, an increase in L-dopa yield of 22.96% was achieved compared with the control (without ascorbate addition) when the process variables, namely buffer pH, L-tyrosine concentration and reaction temperature, were further identified using a two-factorial Plackett–Burman design. Received 5 October 2009/18 January 2010; accepted 1 February 2010 Published as Immediate Publication 1 February 2010, doi:10.1042/BA20090248 © 2010 Portland Press Limited |
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