Dynamic Control Strategy to Produce Riboflavin with Lignocellulose Hydrolysate in the Thermophile Geobacillus thermoglucosidasius

A highly efficient method for genomic deletion across diverse lengths in thermophilic Parageobacillus thermoglucosidasius

Parageobacillus thermoglucosidasius is emerging as a highly promising thermophilic organism for metabolic engineering. The utilization of CRISPR-Cas technologies has facilitated programmable genetic manipulation in P. thermoglucosidasius. However, the absence of thermostable NHEJ enzymes limited the capability of the endogenous type I CRISPR-Cas system to generate a variety of extensive genomic deletions. Here, two thermophilic NHEJ enzymes were identified and combined with the endogenous type I CRISPR-Cas system to develop a genetic manipulation tool that can achieve long-range genomic deletion across various lengths. By optimizing this tool-through adjusting the expression level of NHEJ enzymes and leveraging our discovery of a negative correlation between GC content of the guide RNA (gRNA) and deletion efficacy-we streamlined a comprehensive gRNA selection manual for whole-genome editing, achieving a 100 % success rate in randomly selecting gRNAs. Notably, using just one gRNA, we achieved genomic deletions spanning diverse length, exceeding 200 kilobases. This tool will facilitate the genomic manipulation of P. thermoglucosidasius for both fundamental research and applied engineering studies, further unlocking its potential as a thermophilic cell factory.

Metabolic engineering of Geobacillus thermoglucosidasius for polymer-grade lactic acid production at high temperature

The production and application of biodegradable polylactic acid are still severely hindered by the cost of its polymer-grade lactic acid monomers. High-temperature biomanufacturing has emerged as an increasingly attractive approach to enable low-cost and high-efficiency bulk chemical production. In this study, thermophilic Geobacillus thermoglucosidasius was reprogrammed to obtain optically pure l-lactic acid- and d-lactic acid-producing strains, G. thermoglucosidasius GTD17 and GTD7, by using rational metabolic engineering strategies including pathway construction, by-product elimination, and production enhancing. Moreover, semi-rational adaptive evolution was carried out to further improve their lactic acid synthesis performance. The final strains GTD17-55 and GTD7-144 produce 151.1 g/L of l-lactic acid and 153.1 g/L of d-lactic acid at 60 °C, respectively. In consideration of the high temperature, productive performance of these strains is superior compared to the state-of-the-art industrial strains. This study lays the foundation for the low-cost and efficient production of biodegradable plastic polylactic acid.

A thermostable type I-B CRISPR-Cas system for orthogonal and multiplexed genetic engineering

Thermophilic cell factories have remarkably broad potential for industrial applications, but are limited by a lack of genetic manipulation tools and recalcitrance to transformation. Here, we identify a thermophilic type I-B CRISPR-Cas system from Parageobacillus thermoglucosidasius and find it displays highly efficient transcriptional repression or DNA cleavage activity that can be switched by adjusting crRNA length to less than or greater than 26 bp, respectively, without ablating Cas3 nuclease. We then develop an orthogonal tool for genome editing and transcriptional repression using this type I-B system in both thermophile and mesophile hosts. Empowered by this tool, we design a strategy to screen the genome-scale targets involved in transformation efficiency and established dynamically controlled supercompetent P. thermoglucosidasius cells with high efficiency ( ~ 108 CFU/μg DNA) by temporal multiplexed repression. We also demonstrate the construction of thermophilic riboflavin cell factory with hitherto highest titers in high temperature fermentation by genome-scale identification and combinatorial manipulation of multiple targets. This work enables diverse high-efficiency genetic manipulation in P. thermoglucosidasius and facilitates the engineering of thermophilic cell factories.