A Rotational Slurry Bioreactor Accelerates Biodegradation of A-Fuel in Oil-Contaminated Soil Even under Low Temperature Conditions

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A Rotational Slurry Bioreactor Accelerates Biodegradation of A-Fuel in Oil-Contaminated Soil Even under Low Temperature Conditions

An effective bioaugmentation system for oil-contaminated soil under low-temperature conditions was developed with a rotational slurry bioreactor. Mixtures of two Rhodococcus oil-degraders, strain A and C, which are officially permitted to be used in bioaugmentation in Japan, were inoculated and A-fuel oil was added to a final concentration of 2500 and 5000 mg/kg-slurry. Decomposition tests were carried out for the inoculated samples and non-inoculated samples by rotating at 15 °C, the annual average temperature of Japan. The residue of A-fuel oil and the number of bacteria were measured every two days. After 6 days of treatment, more than 95% of the oil was removed in the inoculated samples, which was more than three times faster than a previous degradation experiment without rotation. A semi-continuous treatment was performed by removing 90% of the treated slurry, then adding the same amount of contaminated slurry into the system without additional degraders. Ninety-four percent of A-fuel oil was successfully degraded after 6 days by this repeated treatment. This could drastically reduce the cost of preparing the degraders. Strikingly, semi-continuous treatment showed oil removal in the non-inoculated samples, indicating that the rotational slurry conditions could efficiently promote biodegradation by indigenous degraders. Our rotational slurry bioreactor accelerated the removal of oil contamination without adding further degraders provides an efficient and cost-effective method of removal of A-fuel oil using a semi-continuous system, which can be used in practical applications in areas with a cooler climate

RNA-seq analysis of lignocellulose-related genes in hybrid Eucalyptus with contrasting wood basic density

Abstract Background Wood basic density (WBD), the biomass of plant cell walls per unit volume, is an important trait for elite tree selection in kraft pulp production. Here, we investigated the correlation between WBD and wood volumes or wood properties using 98 open-pollinated, 2.4 to 2.8 year-old hybrid Eucalyptus (Eucalyptus urophylla x E. grandis). Transcript levels of lignocellulose biosynthesis-related genes were studied. Results The progeny plants had average WBD of 516 kg/m3 with normal distribution and did not show any correlations between WBD and wood volume or components of α-cellulose, hemicellulose and Klason lignin content. Transcriptomic analysis of two groups of five plants each with high (570–609 kg/m3) or low (378–409 kg/m3) WBD was carried out by RNA-Seq analysis with total RNAs extracted from developing xylem tissues at a breast height. Lignocellulose biosynthesis-related genes, such as cellulose synthase, invertase, cinnamate-4-hydroxylase and cinnamoyl-CoA reductase showed higher transcript levels in the high WBD group. Among plant cell wall modifying genes, increased transcript levels of several expansin and xyloglucan endo-transglycosylase/hydrolase genes were also found in high WBD plants. Interestingly, strong transcript levels of several cytoskeleton genes encoding tubulin, actin and myosin were observed in high WBD plants. Furthermore, we also found elevated transcript levels of genes encoding NAC, MYB, basic helix-loop-helix, homeodomain, WRKY and LIM transcription factors in the high WBD plants. All these results indicate that the high WBD in plants has been associated with the increased transcription of many genes related to lignocellulose formation. Conclusions Most lignocellulose biosynthesis related genes exhibited a tendency to transcribe at relatively higher level in high WBD plants. These results suggest that lignocellulose biosynthesis-related genes may be associated with WBD

Additional file 3: of RNA-seq analysis of lignocellulose-related genes in hybrid Eucalyptus with contrasting wood basic density

Figure S1. Correlation between WBD and wood volume (A), Îą-cellulose content (B), Klason lignin content (C) and hemicellulose content (D). (PPTX 84 kb

Additional file 9: of RNA-seq analysis of lignocellulose-related genes in hybrid Eucalyptus with contrasting wood basic density

Table S6. List of transcription factors and mean values of their transcript levels in both plant groups. Arabidopsis homolog names are also listed. (XLSX 19 kb

Additional file 6: of RNA-seq analysis of lignocellulose-related genes in hybrid Eucalyptus with contrasting wood basic density

Table S3. List of cellulose and xylan biosynthesis pathway genes and mean values of their transcript levels in both plant groups. Arabidopsis homolog names are also described. (XLSX 19 kb

Additional file 1: of RNA-seq analysis of lignocellulose-related genes in hybrid Eucalyptus with contrasting wood basic density

Table S1. The total RNA-seq dataset (RPKM > 10). (XLSX 10 kb

Additional file 5: of RNA-seq analysis of lignocellulose-related genes in hybrid Eucalyptus with contrasting wood basic density

Figure S3. Relative transcript levels of CesA2, CesA3, 4CL1, HCT, CSE, F5H, NST1, bHLH1, HD8 and LIM1 genes in the two plant groups measured by qRT-PCR analysis. UBI1 (A) and HST1 (B) genes were used as the reference gene. Double asterisks indicate significant difference at p < 0.01, respectively. (PPTX 55 kb

Additional file 2: of RNA-seq analysis of lignocellulose-related genes in hybrid Eucalyptus with contrasting wood basic density

Table S2. Gene-specific primers used in qRT-PCR. (XLSX 9 kb