Extracellular ligninases production and lignin degradation by Paenibacillus polymyxa.

Bacteria represent an attractive source for the isolation and identification of potentially useful microorganisms for lignin depolymerization, a process required for the use of agricultural waste. In this work, ten autochthonous bacteria isolated from straw, cow manure, and composts were characterized for potential use in the biodelignification of the waste. A comparison of the ability to degrade lignin and the efficiency of ligninolytic enzymes was performed in bacteria grown in media with lignin as a sole carbon source (LLM, 3.5g/L lignin-alkali) and in complex media supplemented with All-Ban fiber (FLM, 1.5g/L). Bacterial isolates showed different abilities to degrade lignin, they decreased the lignin concentration from 7.6 to 18.6% in LLM and from 11.1 to 44.8% in FLM. They also presented the activity of manganese peroxidase, lignin peroxidases, and laccases with different specific activities. However, strain 26 identified as Paenibacillus polymyxa by sequencing the 16S rRNA showed the highest activity of lignin peroxidase and the ability to degrade efficiently lignocellulose. In addition, P. polymyxa showed the highest potential (desirability ≥ 0.795) related to the best combination of properties to depolymerize lignin from biomass. The results suggest that P. polymyxa has a coordinated lignin degradation system constituted of lignin peroxidase, manganese peroxidase, and laccase enzymes.

Inoculation with the mycorrhizal fungus Rhizophagus irregularis modulates the relationship between root growth and nutrient content in maize (Zea mays ssp. mays L.).

Plant root systems play a fundamental role in nutrient and water acquisition. In resource-limited soils, modification of root system architecture is an important strategy to optimize plant performance. Most terrestrial plants also form symbiotic associations with arbuscular mycorrhizal fungi to maximize nutrient uptake. In addition to direct delivery of nutrients, arbuscular mycorrhizal fungi benefit the plant host by promoting root growth. Here, we aimed to quantify the impact of arbuscular mycorrhizal symbiosis on root growth and nutrient uptake in maize. Inoculated plants showed an increase in both biomass and the total content of twenty quantified elements. In addition, image analysis showed mycorrhizal plants to have denser, more branched root systems. For most of the quantified elements, the increase in content in mycorrhizal plants was proportional to root and overall plant growth. However, the increase in boron, calcium, magnesium, phosphorus, sulfur, and strontium was greater than predicted by root system size alone, indicating fungal delivery to be supplementing root uptake.