초록
<P><B>Highlights</B></P><P>► A recombinant Emericella nidulans derived endo-1,4-β-galactanase in Pichia pastoris. ► Determination of pH and temperature optimum, and thermal stability of this enzyme. ► <I>In vitro</I> prebiotic assessment of enzymatically hydrolysed potato galactan oligos.</P> <P><B>Abstract</B></P><P>Potato pulp is a high-volume side-stream from industrial potato starch manufacturing. Enzymatically solubilized β-1,4-galactan-rich potato pulp polysaccharides of molecular weights >100kDa (SPPP) are highly bifidogenic in human fecal sample fermentations <I>in vitro</I>. The objective of the present study was to use potato β-1,4-galactan and the SPPP as substrates for enzymatic production of potentially prebiotic compounds of lower and narrower molecular weight. A novel endo-1,4-β-galactanase from <I>Emericella nidulans</I> (anamorph <I>Aspergillus nidulans</I>), GH family 53, was produced in a recombinant <I>Pichia pastoris</I> strain. The enzyme was purified by Cu<SUP>2+</SUP> affinity chromatography and its optimal reaction conditions were determined to pH 5 and 49°C via a statistical experimental design. The specific activity of the <I>E. nidulans</I> enzyme expressed in <I>P. pastoris</I> was similar to that of an endo-1,4-β-galactanase from <I>Aspergillus niger</I> used as benchmark. The <I>E. nidulans</I> enzyme expressed in <I>P. pastoris</I> generated a spectrum poly- and oligo-saccharides which were fractionated by membrane filtration. The potential growth promoting properties of each fraction were evaluated by growth of beneficial gut microbes and pathogenic bacteria. All the galactan- and SPPP-derived products promoted the growth of probiotic strains of <I>Bifidobacterium longum</I> and <I>Lactobacillus acidophilus</I> and generally did not support the propagation of <I>Clostridium perfringens</I> in single culture fermentations. Notably the growth of <I>B. longum</I> was significantly higher (<I>p</I><0.05) or at least as good on galactan- and SPPP-derived products as fructooligosaccharides (FOS). Except in one case these products did not support the growth of the pathogen <I>Cl. perfringens</I> to any significant extent.</P>