Pectin utilization by the methylotrophic yeast Pichia methanolica

Abstract

The methylotrophic yeastPichia methanolicawas able to grow on pectic compounds, pectin and polygalacturonate, as sole carbon sources. Under the growth conditions used,P. methanolicaexhibited increased levels of pectin methylesterase, and pectin-depolymerizing and methanol-metabolizing enzyme activities. On the other hand,P. methanolicahas two alcohol oxidase (AOD) genes,MOD1andMOD2. On growth on pectin, theP. methanolica mod1Δ andmod1Δmod2Δ strains showed a severe defect in the growth yield, although themod2Δ strain could grow on polygalacturonate to the same extent as the wild-type strain. The expression ofMOD1was detected in pectin-grown cells, but theMOD2-gene expression detected by pectin was much lower than that ofMOD1. Moreover, pectin could induce peroxisome proliferation inP. methanolica, like methanol and oleic acid. These findings showed thatP. methanolicawas able to utilize the methylester moiety of pectin by means of methanol-metabolic enzymes in peroxisomes, and that the functional AOD subunit for pectin utilization was Mod1p inP. methanolica.