Soluble potato starch s 2630

One batch of raw navy beans (Phaseolus vulgaris L.) was procured from a local store in Palmerston North, New Zealand. Pepsin (from porcine gastric mucosa, ≥250 units/mg protein), pancreatin (from porcine pancreas, activity equivalent to 4× USP specifications), invertase (from baker’s yeast (S. cerevisiae), Grade VII, ≥300 units/mg solid), porcine pancreatic α-amylase (from porcine pancreas, type VI-B), soluble potato starch (S-2630), and maltose (S-5885) were purchased from Sigma-Aldrich Ltd., St Louis, MO, USA. Amyloglucosidase (for total dietary fibre and starch assays, 3260 U/mL) was purchased from Megazyme International Ireland Ltd., Wicklow, Ireland. All other chemicals and reagents were of analytical grade. Reverse osmosis (RO) water was used for all experiments.

Commercial granular raw resistant potato starch was from Bauckhof (Rosche, Germany), soluble potato starch (S2630) and granular unmodified wheat starch (S5127) were from Sigma-Aldrich (St. Louis, USA). The granular starches for the liquid or solid media growth experiments were not autoclaved to minimize changes of the native starch granule structure, but the soluble starch comprising was autoclaved and used for the growth phenotype assay on plates. The granular starches were thoroughly washed four times with five consecutive volumes of Milli-Q water, 70% ethanol, Milli-Q water and 70% ethanol at 30 °C with intermittent centrifugation at 5000xg. The residual ethanol was evaporated in a laminar flow bench and each starch substrate was subsequently resuspended in autoclaved growth media and added to make a homogenous suspension in agar plate before solidification. p-Nitrophenyl-α-d-glucopyranoside (PNPG) was from Sigma-Aldrich, and insoluble Blue Starch (iBS) was a custom preparation from Pharmacia (Uppsala, Sweden).