45H-13 |
Lactic acid fermentation-aided hydrolysis of tilapia (Oreochromis niloticus) biomass |
A. M. MARTIN and A. Bezerra. Dept. of Biochemistry, Memorial Univ. of Newfoundland, 300 Prince Philip Dr., Saint John's, NF A1B 3X9, Canada The processing of Tilapia, Oreochromis niloticus - a fish extensively cultivated in tropical regions, produces by-products with potential for conversion into food or feed ingredients. The objective of this work was to study the bioconversion of tilapia into a protein hydrolysate. To decrease the pH and facilitate the action of proteases in the fish, minced tilapia was inoculated with Lactobacillus plantarum, and molasses (15% w/w) was added as the carbohydrate source for lactic acid fermentation. Additional experiments were conducted with formic acid (3% w/w). Triplicate experiments were conducted in 20 L containers, at 30oC, for 30 days. Lipid content was determined after Soxhlet extraction. The Kjeldahl method was used for total nitrogen, and protein content was calculated by multiplying the percentage of nitrogen by 6.25. Amino acids were determined using an Amino Acid Analyzer. Methionine and cysteine were measured separately as methionine sulfone and cysteic acid. Tryptophan was determined by UV absorption. The hydrolysates were mixed with wheat bran (3:1 w/w ratio, respectively) and used in feeding trials of tambaqui (Colossoma macropomum), a promising species for aquaculture. Protein efficiency ratio (PER) and apparent protein digestibility (APD) of the diets were determined. The chemical compositions of both hydrolysates were similar, with the crude protein of the formic acid hydrolysate (14.8% wwb) being slightly higher than that of the lactic acid hydrolysate (12.7 %), due to the dilution effect of the molasses. Compared with the whole tilapia, there was a decrease of 49.6% of tryptophan in the formic acid hydrolysate, but only of 16.0% in the lactic acid hydrolysate, due to its higher pH. Diets based on the latter produced the best results for PER and APD. Based on the satisfactory growth of tambaqui, it can be concluded that tilapia hydrolysate could be utilized as a protein source in feed production.
Session 45H, International: General
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