Valorization Potential of a Novel Bacterial Strain, Bacillus altitudinis RSP75, towards Lignocellulose Bioconversion: An Assessment of Symbiotic Bacteria from the Stored Grain Pest, Tribolium castaneum

Abstract

Bioconversion of lignocellulose into renewable energy and commodity products faces a major obstacle of inefficient saccharification due to its recalcitrant structure. In nature, lignocellulose is efficiently degraded by some insects, including termites and beetles, potentially due to the contribution from symbiotic gut bacteria. To this end, the presented investigation reports the isolation and characterization of cellulolytic bacteria from the gut system of red flour beetle, Tribolium castaneum. Out of the 15 isolated bacteria, strain RSP75 showed the highest cellulolytic activities by forming a clearance zone of 28 mm in diameter with a hydrolytic capacity of ~4.7. The MALDI-TOF biotyping and 16S rRNA gene sequencing revealed that the strain RSP75 belongs to Bacillus altitudinis. Among the tested enzymes, B. altitudinis RSP75 showed maximum activity of 63.2 IU/mL extract for xylanase followed by β-glucosidase (47.1 ± 3 IU/mL extract) which were manifold higher than previously reported activities. The highest substrate degradation was achieved with wheat husk and corn cob powder which accounted for 69.2% and 54.5%, respectively. The scanning electron microscopy showed adhesion of the bacterial cells with the substrate which was further substantiated by FTIR analysis that depicted the absence of the characteristic cellulose bands at wave numbers 1247, 1375, and 1735 cm−1 due to hydrolysis by the bacterium. Furthermore, B. altitudinis RSP75 showed co-culturing competence with Saccharomyces cerevisiae for bioethanol production from lignocellulose as revealed by GC-MS analysis. The overall observations signify the gut of T. castaneum as a unique and impressive reservoir to prospect for lignocellulose-degrading bacteria that can have many biotechnological applications, including biofuels and biorefinery.

Screening of cellulose-degrading yeast and evaluation of its potential for degradation of coconut oil cake

“…The C-O tensile band around 1,243 cm –1 represents hemicellulose and cellulose ( Dar et al, 2021 ). In addition, the peak value was about 1,600 cm –1 , which corresponded to the aromatic ring vibration of lignin, indicating the presence of lignin in the degraded solid ( Lu et al, 2022 ).…”

Exploring the region‐wise diversity and functions of symbiotic bacteria in the gut system of wood‐feeding termite, Coptotermes formosanus, toward the degradation of cellulose, hemicellulose, and organic dyes

“…Inside the gut, the bacterial symbionts exhibit diverse functionalities toward metabolism, supplying nitrogen and vitamins to the host and detoxifying allelochemicals of ingested plants (Warnecke et al ., 2007; Jones et al ., 2019). The symbiotic gut bacteria usually present the metabolic properties that are either low or absent in hosts, thus functioning as “microbial brokers” enabling the termites to overcome recalcitrant diets like lignocellulose (Dillon & Dillon, 2004; Dar et al ., 2021a). Additionally, some bacterial symbionts are known to degrade aromatic hydrocarbons such as lignin or lignin‐mimicking dyes, thus providing additional capabilities to the termite gut (Sun et al ., 2014).…”

Characteristic and activity of cellulolytic bacteria isolated from mangrove soil in Northern Coast of Aceh Province, Indonesia

“…8E1A strain was at pH 7.0 (0.520 U mL -1 ). Dissimilar to Dar et al (2021), B. altitudinis RSP75 showed good cellulolytic activities at pH 5.0, which was the suitable pH for cellulose degradation.…”