Alcalase Bacteria Bacterial fermentation Bacterial fermentations Costs DHA Docosahexaenoic acid Effluents Fish Fish oil Fish protein hydrolysate Fish protein hydrolysates Hydrolysis Lactic acid Marine biorefinery Oils and fats Omega-3 fatty acids Omega-3-fatty acids Polyunsaturated fatty acids Probiotics Proteins Refining Tuna fish oil Tuna fishes Tuna head by-product Tuna head by-products health profession nitrous oxide public health students