The effect of glycerol mixed substrate on the heterologous production of a Rhizopus oryzae lipase in Pichia pastoris system

A recombinant Rhizopus oryzae lipase producing Muts 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-1), maintaining a constant methanol concentration of 2gl-1.At the lowest μ tested (0.02h-1), the specific productivity was 1.23 and 1.61 fold higher and the specific methanol consumption rate (qsMeOH) was 3 and 3.5 fold higher than values obtained when μ was 0.05 and 0.1h-1, respectively. This implies a relation between the qsMeOH 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 μGly and μMeOH 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. © 2011 Elsevier B.V.