Fermentation Of Probiotics Utilizing Tilapia Viscera And Its Application

Tilapa is a type of imported fish. Its by-products of processing have been increasing as the rapidly increasing yield of tilapia in recent twenty years. Only a small part of the by-products (approximately 54% of a whole fish (w/w), among them viscera accounts for 6.8%) was made into feeds and fertilizer with low value, and others were abandoned, resulting in resource waste and environmental pollution. The viscera of tilapia was of good nutritional and economic value as it contains a rich amount of protein, amino acids, fatty acids and various types of active substances. In this research, viscera of tilapia was used as one of the raw material of probiotics (Lactobacillus fermentum, Bifidobacterium lactis and Streptococcus thermophilus) fermentation, and then the fermentation broth was obtained by nutrient and condition optimization. Heavy metal such as Pb, Cd, Cr and Cu of the optimized broth was detected by inductively coupled plasma-atomic emission spectrometry (ICP-AES); antibacterial activity was evaluated by spotting method and oxford plate assay system and the effects were observed by pH, total volatile basic nitrogen (TVB-N) and sensory changes of grass carp slices immersing in the broth after a 10-day storage at low temperature. The results are as followed:(1) Culture medium using viscera of tilapia as one of the ingredients (substituted of nitrogen source and vitamin) was used in probiotics (Lactobacillus fermentum, Bifidobacterium lactis and Streptococcus thermophilus) fermentation (viscera:fernentaion broth (w:v) was 3.33%,13.33% and 1.67%). After optimization of nutrient and condition, the viable counts of each kind of probiotics were about 109 CFU/mL,108 CFU/mL and 108 CFU/mL. In general, culture medium with viscera of tilapia as material can simplify the constituent and lower the cost, and meanwhile obtain the same number of viable cell count or even a little more than commercial media. It shows significant and promosing in application.(2) The result of heavy metal detection showed that, no Cd and Cu and only few of Cr and Pb were found inside the fermentation broth. The result was within the allowable range of industry standard of agriculture department NY5073-2006. So it can be used as a reference for appliance of the viscera fermentation broth.(3) The result of antibacterial activities showed that, three kinds of fermentation broth especially the lactobacillus borth can inhibit the growth of Escherichia coli and salmonella. The antibacterial circle diameter of lactobacillus broth reached to 29.0 mm and 27.5 mm respectively. For the prohibition of pseudomonas growth, the bifidobacteria fermentation broth has showed a certain anti-effect, while lactobacillus and streptococcus fermentation broth hasn't.(4) The result of antisepsis showed that:the fermentation broth can inhibit the TVB-N of immersing grass carp slices in late storage (the sixth to tenth day) comparing to the control group. However, the inhibition effect was not so significant possibly due to the lack of observation time.This research has offered a reference method for the preparation of probiotics products using viscera of tilapia as raw material.