Composting of Vegetable Waste Using Microbial Consortium and Biocontrol Efficacy of Streptomyces Sp. Al-Dhabi 30 Isolated from the Saudi Arabian Environment for Sustainable Agriculture

Resumo

Foram isolados na planta de tomate trinta e sete Actinomycetes associados à raiz para promover o crescimento das plantas. Destes, dez foram selecionados para solubilização de fosfato, produção de sideróforos e ácido indolacético. De dez, oito Actinomycetes solubilizaram fosfato, enquanto que Streptomyces sp. Al-Dhabi 30 apresentou melhor atividade (43,1 mg/dL). Actinomicetos produziram sideróforo e a concentração variou entre 1,6 e 42,1 μg/mL. Streptomyces sp. Al-Dhabi 30 mostrou a capacidade de produzir uma quantidade máxima de ácido indolacético (AIA) (43 μg/mL), quitinase (43,1 U/mL), celulase (67 U/mL) e protease (121 U/mL) do que outras cepas. Além disso, resíduos vegetais foram usados como material a granel para compostagem usando Streptomyces sp. Al-Dhabi 30 junto com o consórcio microbiano. O teor de nitrogênio total foi de 3,8% no composto inoculado com Streptomyces sp. Al-Dhabi 30, enquanto 2,7% de nitrogênio orgânico foram detectados no controle. No resíduo vegetal composto, a razão C:N foi de 10,07, enquanto que no controle foi de 17,51. O resíduo vegetal compostado com Streptomyces sp. Al-Dhabi 30, Lactobacillus plantarum ATCC 33222 e Candidautilis ATCC 9950 apresentaram atividade antagônica e o composto suplementado aumentou a altura da raiz e o peso total das plantas de tomate. Estes achados sugerem claramente o uso de Streptomyces sp. Al-Dhabi 30 como um agente biocontrol potencial.

Abstract

Thirty-seven root-associated Actinomycetes were isolated from the tomato plant for plant growth promoting activity. Among these, ten were selected for phosphate solubilisation, the production of siderophores, and indole acetic acid. Out of ten, eight Actinomycetes solubilised phosphate, whereas, Streptomyces sp. Al-Dhabi 30 showed better activity (43.1 mg/dL). Actinomycetes produced siderophore and the concentration ranged between 1.6 and 42.1 μg/mL. Streptomyces sp. Al-Dhabi 30 showed the ability to produce a maximum amount of indole acetic acid (IAA) (43 μg/mL), chitinase (43.1 U/mL), cellulase (67 U/mL), and protease (121 U/mL) than other strains. Further, vegetable waste was used as the bulk material for composting using Streptomyces sp. Al-Dhabi 30 along with microbial consortium. Total nitrogen content was 3.8% in Streptomyces sp. Al-Dhabi 30 inoculated compost, whereas 2.7% organic nitrogen was detected in the control. In the compost vegetable waste, the C:N ratio was 10.07, whereas it was 17.51 in the control. The vegetable waste composted with Streptomyces sp. Al-Dhabi 30, Lactobacillus plantarum ATCC 33222, and Candidautilis ATCC 9950 showed antagonistic activity and the supplemented compost enhanced shoot, root height, and total weightin tomato plants. These findings clearly suggest the use of Streptomyces sp. Al-Dhabi 30 as a potential biocontrol agent.