Characterization and genomic analysis of kraft lignin biodegradation by the beta-proteobacterium Cupriavidus basilensis B-8

Abstract

BackgroundLignin materials are abundant and among the most important potential sources for biofuel production. Development of an efficient lignin degradation process has considerable potential for the production of a variety of chemicals, including bioethanol. However, lignin degradation using current methods is inefficient. Given their immense environmental adaptability and biochemical versatility, bacterial could be used as a valuable tool for the rapid degradation of lignin. Kraft lignin (KL) is a polymer by-product of the pulp and paper industry resulting from alkaline sulfide treatment of lignocellulose, and it has been widely used for lignin-related studies.ResultsBeta-proteobacterium Cupriavidus basilensis B-8 isolated from erosive bamboo slips displayed substantial KL degradation capability. With initial concentrations of 0.5–6 g L-1, at least 31.3% KL could be degraded in 7 days. The maximum degradation rate was 44.4% at the initial concentration of 2 g L-1. The optimum pH and temperature for KL degradation were 7.0 and 30°C, respectively. Manganese peroxidase (MnP) and laccase (Lac) demonstrated their greatest level of activity, 1685.3 U L-1 and 815.6 U L-1, at the third and fourth days, respectively. Many small molecule intermediates were formed during the process of KL degradation, as determined using GC-MS analysis. In order to perform metabolic reconstruction of lignin degradation in this bacterium, a draft genome sequence for C. basilensis B-8 was generated. Genomic analysis focused on the catabolic potential of this bacterium against several lignin-derived compounds. These analyses together with sequence comparisons predicted the existence of three major metabolic pathways: β-ketoadipate, phenol degradation, and gentisate pathways.ConclusionThese results confirmed the capability of C. basilensis B-8 to promote KL degradation. Whole genomic sequencing and systematic analysis of the C. basilensis B-8 genome identified degradation steps and intermediates from this bacterial-mediated KL degradation method. Our findings provide a theoretical basis for research into the mechanisms of lignin degradation as well as a practical basis for biofuel production using lignin materials.

Production of Ligninolytic Enzymes by Newly Isolated Bacteria from Palm Oil Plantation Soils

“…Based on the present work, Bacillus sp. SHC1 can produce a maximum MnP at 2313.4 U/L, which is higher than for Cupriavidus basilensis B-8 at 1685.3 U/L (Shi et al 2013). However, the MnP activity from Comamonas sp.…”

“…B-9 is at 1250 U/L based on Chen et al (2012). Shi et al (2013) reported that Cupriavidus basilensis B-8 can produce Lac up to 815.6 U/L. Based on the present work, Bacillus sp.…”

“…All solutions were prepared in deionized water. Kraft lignin used in this study is a polymeric lignin alkali material from the pulp and paper industry resulting from alkaline sulfide treatment of lignocelluloses which has been widely used for lignin-related studies (Shi et al 2013). Oil palm empty fruit bunch (OPEFB) was obtained from Sri Ulu Langat Palm Oil Mill in Dengkil, Selangor, Malaysia.…”

“…There was a decrease in ligninolytic activity with an increase in pH and complete inactivation shown at pH 9. Shi et al (2013) reported an alkaline pH range for the growth of Cupriavidus basilensis, which is a lignin-degrading bacterium. The MnP enzyme activity was optimum at pH 8 for Bacillus sp.…”

“…In previous studies, most of the isolated ligninolytic bacteria could only produce two main ligninolytic enzymes, especially a combination of MnP and Lac enzyme production (Shi et al 2013;Chen et al 2012 andOliveira et al 2009). Meanwhile, in this study, all three isolated strains produced all three main ligninolytic enzymes: LiP, MnP, and Lac.…”