Enhanced Low-Temperature Corn Straw Degradation Using a Synthetic Microbial Mixture

TL;DR

A synthetic mix of three bacteria can effectively break down corn straw at low temperatures, improving soil fertility in cold regions.

Contribution

A novel low-temperature synthetic microbial mixture for efficient corn straw degradation is developed and tested.

Findings

The three-strain mixture achieved a 30.93% straw degradation rate at 12°C.

Optimized conditions increased CMCase activity to 24.51 U/mL at 12°C.

The mixture shows potential for improving straw utilization in cold regions.

Abstract

The structural stability of lignocellulosic fibers in crop straw presents a significant challenge to its short-term biodegradation in natural environments, particularly in the cold regions of northern China. To isolate low-temperature straw-degrading bacteria, we selectively enriched microorganisms from straw-amended soils using lignocellulose as the sole carbon source. Three strains were isolated and identified: Stenotrophomonas sp. X24, Flavobacterium sp. X26, and Erwiniaceae bacterium X27. These strains were capable of growth and maize straw degradation within a 4–20 °C range and exhibited key cellulolytic activities (CMCase, FPase, and β-glucosidase). A synthetic three-strain mixture was assembled by combining these isolates in equal proportions. Solid-state fermentation (12 °C, 45 days) was used to assess straw degradation efficacy, while separate enzyme production experiments (12 °C, 3 days) were conducted to evaluate key cellulolytic activities and subsequently optimize culture conditions. The three-strain mixture achieved a net straw degradation rate of 30.93 ± 1.05%. Furthermore, optimization of culture conditions enhanced the carboxymethyl cellulase activity (CMCase) to a maximum of 24.51 ± 0.97 U/mL. The study demonstrates that the three-strain synthetic microbial mixture effectively degrades straw at low temperatures, offering a promising microbial resource to improve straw utilization and soil fertility in cold regions.

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