Scaled-up bioconversion of fish waste to liquid fertilizer using a 5 L ribbon-type reactor.

A scaled-up conversion process of fish waste to liquid fertilizer was performed in a 5 L ribbon-type reactor. Biodegradation was performed by inoculation of autoclaved fish waste with 5.84 × 10(5) CFU mL(-1) of mixed microorganisms for 96 h. As a result, the pH changed from 6.92 to 5.72, the cell number reached 7.28 × 10(5) CFU mL(-1), and approximately 430 g (28.3%) of fish waste was degraded. Analyses indicated that the 96 h culture of inoculated fish waste possessed comparable fertilizing ability to commercial fertilizers in hydroponic culture with amino acid contents of 6.91 g 100 g(-1). Therefore, the scaled-up production achieved a more satisfactory fish waste degradation rate (3.61 g h(-1)) than the flask-scale production (0.24 g h(-1)). The biodegraded broth of fish waste at room temperature did not undergo putrefaction for 6 months due to the addition of 1% lactate.

Identification and characterization of microorganisms from earthworm viscera for the conversion of fish wastes into liquid fertilizer.

Five bacteria isolated from earthworm viscera and identified as Brevibacillus agri, Bacillus cereus, Bacillus licheniformis, and Brevibacillus parabrevis by 16S rRNA sequencing were employed in the conversion of fish wastes generated from a restaurant specializing in sliced raw fish into fertilizer. Within 120h after inoculation of autoclaved fish waste with 5.15 x 10(5) CFU ml(-1) mixed isolates, the amount of dry sludge decreased from 29.4 to 0.2g, the pH changed from 7.05 to 5.70, and the cell number reached 6.45 x 10(5) CFU ml(-1). Analyses of an 84-h culture of inoculated fish waste indicated low phytotoxicity in a seed germination test, an amino acid content of 5.71 g 100 g(-1), a low concentration of heavy metals (Pb, As, Cd, Hg, Cr, Cu, Ni and Zn), and a N/P/K level of 2.33%. Therefore the converted fish waste has the potential for use as liquid fertilizer, although the low NPK level is a concern. This is the first demonstration of the reutilization of fish wastes as a liquid fertilizer.