Feed grain improvement through biopreservation and bioprocessing

Fermentation is an environmentally friendly method to improve feed quality. Fermented liquid feed and airtight stored moist crimped cereal grain systems that are of increasing importance in agricultural practice were studied. Both rely on spontaneous microbial developments with poorly understood population dynamics, resulting in unpredictable final quality. Temperature, fermentation time and ingredients affected final properties of the feed. Molecular-based species identification showed that microbial populations changed, even when total viable counts were stable. Moisture contents in farm-stored crimped cereal grain were mostly below recommended values, resulting in insufficient lactic acid formation and growth of undesirable microbes. Adding starter cultures to fermentation systems influenced microbial populations. A grass silage lactic acid bacteria starter culture was added to liquid feed fermentations. Lactobacillus plantarum of the starter consortium grew well, but Lactobacillus panis from the feed ingredients dominated both inoculated and non-inoculated fermentations. The starter culture did not influence yeast populations. Starter strains should be adapted to the system and may include appropriate yeasts. The lactic acid bacteria Lactobacillus fermentum, L. panis and Pedicoccus pentosaceus, and the yeasts Pichia fermentum and Pichia anomala may be included in such starter cultures. Adding the biocontrol yeast P. anomala to moist crimped cereal grain decreased numbers of undesirable moulds and reduced Enterobacteriaceae by 5 log units during storage. Feeding animals with P. anomala inoculated grain did not adversely affect performance, but only marginally improved weight gain. The yeast contribution to protein content was insufficient to describe the grain as protein feed. This is possibly due to cell density dependent growth inhibition of the yeast, as maximum P. anomala levels on grain, regardless of treatments, never exceeded 8.5 log units. Inoculation of P. anomala with high phytase activity into crimped cereal grain reduced grain phytate levels. Bound phosphorus, in the form of inositol phosphates, was not detected in any of the liquid diets after fermentation

Microbial populations during maize storage in Cameroon

Key microbiota of maize kernels from two farms in Cameroon were characterised at harvest and during five months of drying / storage in firewood kitchens. Moulds populations shifted from Fusarium sp. to Penicillium and Aspergillus during drying, and aflatoxigenic moulds were absent. Lactic acid bacteria (Lactobacillus plantarum, Leuconostoc citreum) were only present earlier on, and Enterobacteriaceae became dominant. Common yeasts were Candida quercitrusa (early storage) and Meyerozyma guilliermondii (late storage). Strains of L. plantarum and M. guilliermondii are known to inhibit mould growth and could be used in an energy-efficient system for moist-storage of maize kernels.Keywords: Maize, mycotoxins, mould, yeast, lactic acid bacteria, biocontro

Population Diversity of Yeasts and Lactic Acid Bacteria in Pig Feed Fermented with Whey, Wet Wheat Distillers' Grains, or Water at Different Temperatures▿

The diversity of populations of yeast and lactic acid bacteria (LAB) in pig feeds fermented at 10, 15, or 20°C was characterized by rRNA gene sequencing of isolates. The feeds consisted of a cereal grain mix blended with wet wheat distillers' grains (WWDG feed), whey (W feed), or tap water (WAT feed). Fermentation proceeded for 5 days without disturbance, followed by 14 days of daily simulated feed outtakes, in which 80% of the contents were replaced with fresh feed mixtures. In WWDG feed, Pichia galeiformis became the dominant yeast species, independent of the fermentation temperature and feed change. The LAB population was dominated by Pediococcus pentosaceus at the start of the fermentation period. After 3 days, the Lactobacillus plantarum population started to increase in feeds at all temperatures. The diversity of LAB increased after the addition of fresh feed components. In W feed, Kluyveromyces marxianus dominated, but after the feed change, the population diversity increased. With increasing fermentation temperatures, there was a shift toward Pichia membranifaciens as the dominant species. L. plantarum was the most prevalent LAB in W feed. The WAT feed had a diverse microbial flora, and the yeast population changed throughout the whole fermentation period. Pichia anomala was the most prevalent yeast species, with increasing occurrence at higher fermentation temperatures. Pediococcus pentosaceus was the most prevalent LAB, but after the feed change, L. plantarum started to proliferate. The present study demonstrates that the species composition in fermented pig feed may vary considerably, even if viable cell counts indicate stable microbial populations