Kajian rasio C/N terhadap produksi bioinsektisida dari Bacillus thuringiensis subsp. aizawai menggunakan substrat limbah cair tahu dan air kelapa

Abstract

Bioinsecticide is an active substance from biological agent that kills insects and disease vector. Bioinsecticide or microbial insecticide can be developed from bacteria, virus, mushroom, and protozoa. Bacteria that often used to produce bioinsecticide is Bacillus thuringiensis (B.t). Bacillus thuringiensis subsp. aizawai (B.t.a) as one of Bacillus thuringiensis species produces crystal protein called delta endotoxin (δ-endotoxin). As other B.t crystal protein, this crystal protein is specifically toxic to larvae Lepidoptera and Diptera. Bioinsecticide is an alternatif solution, because it cannot cause pests resistance, does not make residue to the environment and does not kill non target organisms. This research aims to produce an active material bioinsecticide that is produced by B.t.a using tofu liquid waste and coconut water, which is cheap material can be used as nitrogen and carbon sources and it has protein, vitamin, mineral that are needed by microorganism to grow. Coconut water as fermentable sugar in fermentation bioinsecticide. The specific objective of this research is to obtain the best media formulation with optimal C/N ratio for bioinsecticide production. Carbon-nitrogen ratios in this research are A (3:1), B (5:1), C(7:1), D (9:1), and E (11:1), with 80 : 20 composition of liquid waste of industrial tofu and coconut water, the starter added 10 (%v/v) and cultivation time during 0-72 hours. The highest toxicity of the product can be resulted through bioassay test to Crocidolomia pavonana (C. binotalis) larvae instar-II. The pH value and weight of dry biomass during cultivation was increased while total sugars and OD (Optical Density) is decreased. Range of pH value from 6.5-7.96. For cultivation 0 hours the highest of dry cell biomass is media A (C/N=3:1) 0.60 g/L whereas the lowest is media B (C:N=5:1) and C (C/N=7:1) 0.40 g/L and for cultivation 72 hours the highest of biomass is media C (C/N=7:1) 15.90 g/L whereas the lowest is media A (C/N=3:1) 7.55 g/L. For cultivation 0 hours the highest OD is media D (C/N=9:1) 0.0214 and the end of cultivation the highest OD is media B (C/N=5:1) 2.91. The highest total plate count (TPC) is media C (C/N=7:1) 2.8 x 108 cell/ml or 7.40 cfu/ml in cultivation 48 hours whereas the lowest is media B (C/N=5:1) 1.19 x 107 cell/ml or 6.68 cfu/ml in cultivation 0 hours. The highest viable spore count (VSC) is media D (C/N=9:1) 5.63 x 106 spore/ml in cultivation 48 hours whereas the lowest is media C (C/N=7:1) 2.85x 106 spore/ml in cultivation 24 hours. The highest level toxicity (LC50) is media C (C/N=7:1) 0.01 mg/L in cultivation 48 hours and potential product is 80,000 IU/mg. The level toxicity (LC50) is contrary to potential product.