Novel Nutritional And Biotechnological Approaches To Convert Defatted Microalgal Biomass And Poultry Feathers Into Highly Sustainable Feed Proteins
With our global population on the rise, there is a need not only for alternative sources of energy for both humans and animals, but also for alternative food sources to maintain food security. Microalgae from biofuel production and poultry feather waste are both rich in protein, and stand as promising candidates for supplementation into animal diets as protein-rich feed additives. In doing so, the corn and soybean meal that traditionally make up the majority of an agricultural animal's diet, may be re-allocated for human consumption. Additionally, developing new uses for a waste product of the biofuel industry (microalgae) and poultry industry (feathers) would help alleviate environmental pollution. We aimed to 1) determine the nutritional potential of supplementing microalgae biomass into the diets of weanling pigs, without negatively affecting their growth performance or health, and 2) improve the digestibility of poultry feathers in vivo through the use of cloned and expressed microbial enzymes in in vitro feather hydrolysis. Protein-rich microalgal biomass from biofuel production stands as a promising new animal feed source, and may serve as an alternative to corn and soybean meal (SBM) in animal diets. Our objective was to determine potential and limitation of a new diatom microalgal species Staurosira sp (full-fat microalgae) and its defatted algal biomass generated from biofuel production in replacing SBM and corn in diets for weanling pigs. Two experiments were conducted. In the first experiment pigs were fed a corn and SBM basal diet (BD), BD + 7.5% defatted algae replacing SBM, and BD + 7.5% or 15% de-fatted algae replacing corn and SBM for 6 wk. We found that the inclusion of algae in the diet to replace a significant portion of SBM lowered the average daily gain and feed efficiency of the pigs. Feeding pigs 15% defatted algae resulted in lower fecal microminerals Cu, Se, and Zn. The health status of the pigs, as determined by plasma biochemical assays, was not negatively affected. It was hypothesized that either the micromineral deficiencies, or the acid:base balance of the algae biomass negatively affected the growth performance of the pigs. A second study was conducted on the full-fat algae with and without the inclusions of either fumaric acid or the minerals found to be limited in Experiment 1. The inclusion of fumaric acid with algae alleviated the growth losses of algae fed to pigs alone. It was feasible to supplement 7.5% de-fatted algae or 10% full-fat with an organic acid for a replacement of the same amount of corn and SBM in diets for weanling pigs, without adverse effect on growth performance, biochemical status, or fecal excreta. Previous research on hydrolyzing keratinous feathers suggests that microbial proteases and reductases may be key players in their effective degradation. We describe the first heterologous protein expression of 3 predicted serine proteases and 7 predicted thioredoxin disulfide reductases from Streptomyces fradiae var. k11. The in vitro feather hydrolysis assay showed that the inclusion of reductases and proteases, with the additions of a known chemical reducing agent ([beta]-mercaptoethanol) and protease (Proteinase K), apply a synergistic effect in feather keratinolysis. As such, these cloned and expressed enzymes have promising potential for industrial uses and feather keratin.
microalgae; biomass; feather; hydrolysis; protease; reductas
Wilson, David B; Cherney, Debbie Jeannine
M.S., Animal Science
Master of Science
dissertation or thesis