Optimization of waste combinations during decomposition of domestic organic waste using the response surface methodology

Accumulation of domestic organic waste needs to be processed because it can cause negative effects on the environment. Domestic organic waste can be decomposed into high value products of secondary metabolite by using bacteria like biopesticide. Composition of domestic organic waste as a substrate can affect the decomposition of that waste. This research aims to investigate the optimum composition of domestic waste and additional materials in treating domestic organic waste by using Streptomyces sp GMR-22. Composition of the waste and additional materials was determined by proximate nutrition factors of the ash, protein, fat, and carbohydrate contents and optimized by using response surface methodology (RSM). The temperature and moisture was set to 37°C and 60 respectively. The response was demonstrated by the number of Streptomyces sp GMR-22 on the eight day of the solid-state fermentation (SSF) process. The results show that the highest cell number of Streptomyces sp GMR-22 on eight days was resulted from the combination of 5.25 g ash, 5.5 g protein, 1.5 g fat, and 41 g carbohydrate on resulting 2,8 x 10⁹ cells/gram of substrate. The RSM results indicated that carbohydrate and protein contents were the main factors on the growth of Streptomyces sp. GMR-22. On the other hand, ash had a low significance and fat had no significant effect. In the processing of domestic organic waste through SSF which was based on the proximate value, the RSM results can be used to determine nutrition priorities that must be met.