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Production of L-aspartic acid by biotransformation and recovery using reverse micelle and gas hydrate methods

Aydogan, Oezlem
Bayraktar, Emine
Parlaktuna, Mahmut
Mehmetoglu, Tanju
Mehmetoglu, Uelkue
L-Aspartic acid (L-Asp) was produced using Escherichia coli (ATCC 11303), and its recovery from the reaction mixture was studied using reverse micelle and gas hydrate methods. The effect of initial substrate concentration on L-Asp production was also investigated, and inhibition was shown to occur above 0.75 mol L-1. The values of the kinetic constants were determined as r(max) = 2.33 x 10(-4) mol L-1 min(-1), K-M = 0.19 mol L-1, and K-ss = 3.98 mol L-1. The reverse micelle phase used for extraction contained Aliquat-336, 1-decanol and isooctane, and a micro-injection technique was used for extraction of L-Asp. The reverse micelle system is a useful technique for obtaining small particle sizes, which can be used for the synthesis of nanoparticle biomolecules. Recovery of L-Asp from reverse micelles using CO2 hydrates was carried out, giving a recovery of 55%. The formation of CO2 hydrate from the reverse micelle solution breaks the micelle by reducing the amount of water in the micelle structure, thus precipitating the L- Asp.