Biodegradação e formulação de meio de cultura usando escama de peixe como substrato

Abstract

The increasing industrialization of fish has generated large amounts of solid waste. Among these residues are scales, abundant material, rich in proteins and low cost, which are often discarded incorrectly, causing environmental damage. The transformation of waste into byproducts is the basis of sustainable development and ensures processes that are more economical and have less environmental impact. The nutritional requirements of microbial cells have been supplied in research laboratories and / or clinics by different culture media, however, the high value of these means make it difficult to perform laboratory activities. The objective of the present work was to investigate the biotechnological potential of bacteria of the genus Bacillus in the degradation of fish scales, as well as to test different formulations of culture medium based on fish scale in substitution to the formulation of means of commercial cultures in the growth of Bacillus Subtilis. For this the work was developed in two stages. In stage 1 (degradation assays) 1 mL inoculum (108 UFC/mL) of the Bacillus isolates (B1, B2, B3 e B4) were transferred to Erlenmeyer's 250 mL containing 60 mL of minimal mineral medium (supplemented with 1% glucose and 1% yeast extract) and 1g of fish scale, incubation for six days at 125 rpm and temperature controlled at 37 ° C. In addition, the pH was measured at the beginning and at the end of the degradation. In the second step, two culture media were formulated with scales, C1 broth (5 g of crushed flakes, 5 g of glucose, 1.5g of yeast extract, 5 g of sodium chloride and 1000 ml of distilled water) and C2 Hydrolysed from the degradation step). The efficiency of the formulated media was presented by means of the specific growth rate μ (h-1) and the generation time, tg (h) of Bacillus subtilis (B1). The degradation yield using whole scales by isolates of the genus Bacillus ranged from 12 to 21%. In relation to the degradation using crushed scales, the yield was higher, varying from 13 to 26%. The isolate that presented the highest yield in the degradation using whole scale was the B4 and in the degradation using crushed scale was the isolate B1. It was also verified that the highest pH increase (7,8) occurred with the isolate B1, which presented higher rate of scale degradation. In the fish stock broth (broth C1), the growth of B. subtilis (B1) showed a higher specific growth rate (0.839 h-1), differing statistically from the other broths and lower generation time (49.57 min). However, growth in fish scale protein hydrolyzate broth (C2 broth) showed the most defined growth phases and a transition from the exponential phase to the more gradual stationary phase. It was possible to conclude that the Bacillus strains presented degradation capacity of recalcitrant substrates based on scale and that the bioconversion of this material through fermentation is an alternative to reduce the amount of industrial solid waste, being possible the use of fish scale in the formulation of culture media in place of the commercial means available on the market today.