Effect of micro-organism and particle size on fermentation of sorghum and maize for poultry feed

Abstract

A study was conducted to investigate the effect of particle size and micro-organism on fermentation of sorghum and maize for poultry feed. Sorghum (Sorghum bicolour L. Moench) and maize were milled in a hammer mill and separated into coarse, medium, fine and very fine particles sizes with a stack of sieves of apertures 2.5 mm, 850 μm and 500 μm, from the first to the last sieve and ending in a pan with the very fine particles. Samples were weighed into 100 g sachets and irradiated using ⁶⁰Co at 25 kGy γ-radiation. Grains were fermented with sterile distilled water for 24 h at a ratio of 1 feed:1.4 water and inoculated with 0.01 ml of an overnight culture of De Man, Rogosa and Sharpe (MRS) broth containing Pediococcus acidilactici (PA1) or Lactobacillus plantarum (SLP) (ca 10⁹ cfu/ml). The medium was incubated at 30°C simultaneously with a control treatment without lactic acid bacteria (LAB). Subsamples were collected aseptically at the beginning of the fermentation (0 h) and at 4, 8, 24 h after fermentation for pH, sugar and organic acids analysis. Significant reductions in the pH of maize and sorghum for LAB treatments (PA1 and SLP) were evident after 8 hours of fermentation. Twenty four hour lactic acid concentrations from coarse particle size fermentations were not significantly different from concentrations in the medium and fine particle size fermentations. The choice of LAB did not affect the concentration of lactic acid for any particle size. However, acetic acid production from fermentation with PA1 was significantly higher (P<0.01) than the concentration obtained with SLP. Results suggest that moderate grain processing may be enough to permit production of biosafe levels of lactic acid in fermented feed for poultry birds.

Keywords: Fermentation, lactic acid bacteria, maize, particle size, sorghum

African Journal of Biotechnology Vol. 12(26), pp. 4147-4157