The effects of rice fibre on probiotic fermentation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology and Microbiology at Massey University, Palmerston North, New Zealand

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The role of rice fibre in stimulating the growth and SCFA (Short Chain Fatty Acid) formation by human faecal micro-flora and individual probiotics and co-cultures was investigated. The effects of environmental factors on the adhesion of probiotics on rice fibre were also evaluated. Fibre fractions of rice enhanced the growth of human colon microflora (Bifidobacterium species and Lactobacillus species) with a corresponding increase in the quantity of SCFA produced. However, individual microorganisms showed different preferences for different rice varieties and specific fractions of rice fibre. Pure cultures of the genus Bifidobacterium and genus Lactobacillus fermented rice fibre fractions irrespective of the rice variety. However, the genus Bifidobacterium produced more SCFA than genus Lactobacillus. Co-cultures of Bifidobacteria and Lactobacilli showed a greater ability than pure cultures to digest fibre and form SCFA, indicating synergism. Co-cultures used the fibre fractions irrespective of the rice variety. All microflora from mixed faecal inocula, pure and combinations of probiotic cultures showed a preference for total dietary fibre than insoluble and soluble dietary fibre fractions based on fermentation and SCFA production. All cultures tested, including human faecal cultures, pure cultures and co-cultures, produced more acetate than propionate and butyrate. Pure cultures and co-cultures adhered to rice fibre. Adhesion was influenced by environmental factors and is believed to play a role in the fermentation of rice fibre. Rice fibre is a suitable substrate for probiotic microflora.
Probiotics, Bifidobacterium, Lactobacillus, Short chain fatty acid, Microflora