초록
A recombinant Rhizopus oryzae lipase producing Mut<SUP>s</SUP>Pichia pastoris strain was used as a model organism to study the effect of mixed substrates (glycerol and methanol) on the specific product productivity. Different fed-batch cultivations were performed under three constant specific growth rates (0.02, 0.05 and 0.1h<SUP>-1</SUP>), maintaining a constant methanol concentration of 2gl<SUP>-1</SUP>. At the lowest μ tested (0.02h<SUP>-1</SUP>), the specific productivity was 1.23 and 1.61 fold higher and the specific methanol consumption rate (q<SUB>sMeOH</SUB>) was 3 and 3.5 fold higher than values obtained when μ was 0.05 and 0.1h<SUP>-1</SUP>, respectively. This implies a relation between the q<SUB>sMeOH</SUB> and the specific productivity, yielding higher specific productivities whenever the consumption of methanol is higher. Although glycerol was maintained under limiting conditions in all μ tested, when the relation between the μ<SUB>Gly</SUB> and μ<SUB>MeOH</SUB> was larger than 4, an important decrease on the maximal activity value was observed. Finally, a comparison under the same conditions using glycerol or sorbitol as co-substrates was also performed, obtaining better specific productivity when sorbitol was used. In addition, protease activity was detected when glycerol was used as co-substrate.