Thermo-resistant enzyme-producing microorganisms isolated from composting

Abstract

Organo-mineral fertilizers supplemented with biological additives are an alternative to chemical fertilizers. In this study, thermoresistant microorganisms from composting mass were isolated by two-step procedures. First, samples taken at different time points and temperatures (33 days at 52 ºC, 60 days at 63 ºC, and over 365 days at 26 ºC) were pre-incubated at 80 oC for 30 minutes. Second, the microbial selection by in vitro culture-based methods and heat shock at 60 oC and 100 oC for 2h and 4h. Forty-one isolates were able to grow at 60 °C for 4h; twenty-seven at 100 °C for 2h, and two at 100 °C for 4h. The molecular identification by partial sequencing of the 16S ribosomal gene using universal primers revealed that thirty-five isolates were from eight Bacillus species, one Brevibacillus borstelensis, three Streptomyces thermogriseus, and two fungi (Thermomyces lanuginosus and T. dupontii). Data from amylase, phytase, and cellulase activity assays and the enzymatic index (EI) showed that 38 of 41 thermo-resistant isolates produce at least one enzyme. For amylase activity, the highest EI value was observed in Bacillus licheniformis (isolate 21C2, EI= 4.11), followed by Brevibacillus borstelensis (isolate 6C2, EI= 3.66), Bacillus cereus (isolate 18C2, EI= 3.52), and Bacillus paralicheniformis (isolate 20C2, EI= 3.34). For phytase, the highest EI values were observed for Bacillus cereus (isolate 18C2, EI= 2.30) and Bacillus licheniformis (isolate 3C1, EI= 2.15). Concerning cellulose production, B. altitudinis (isolate 6C1) was the most efficient (EI= 6.40), followed by three Bacillus subtilis (isolates 9C1, 16C2, and 19C2) with EI values of 5.66, 5.84, and 5.88, respectively, and one B. pumilus (isolate 27C2, EI= 5.78). The selected microorganisms are potentially useful as a biological additive in organo-mineral fertilizers and other biotechnological processes.

A new source of bacterial myrosinase isolated from endophytic Bacillus sp. NGB-B10, and its relevance in biological control activity

“…We do not have a clear explanation for the high thermal stability of myrosinase under this investigation which is higher than that reported so far for other microbial myrosinases, even those purified from fungi (Rakariyatham et al 2005 ). However, it can be attributed to the nature of its source, as the genus Bacillus is known as a potential source of producing thermostable enzymes (Cotta et al 2021 ; Aktayeva et al 2022 ). Additionally, the myrosinase in this study appears to prefer alkaline conditions (with an optimal pH of 8.00) compared to myrosinases previously isolated from other bacteria that had optimal pH values in the range of 6.0–6.6 (Tie et al 2021 ; Cebeci et al 2022 ).…”

Metagenomic-Metabolomic Mining of Kinema, a Naturally Fermented Soybean Food of the Eastern Himalayas

“…Though B. cereus is a food-borne pathogen, its pathogenicity varies from harmless to lethal (Kavanaugh et al, 2022). B. borstelensis was also an abundant rod-shaped and Gram-positive bacterium in kinema samples, which is mostly thermoresistant, enzyme producing, and alkaline tolerant (Cotta et al, 2021). About 121 species of LAB (<1% relative abundance) were also detected from kinema samples, showing their co-existence with Bacillus spp.…”