Identification and characterization of lignin depolymerization enzymes in Bacillus subtilis strain S11Y isolated from a tropical environment in Malaysia.

Biological pretreatment using microbial enzymes appears to be the most promising pre-treatment technology for the breakdown of recalcitrant lignin structure. This research focuses on the identification and characterization of lignin-depolymerizing enzymes in Bacillus subtilis strain S11Y, previously isolated from palm oil wastes in Malaysia. The draft genome sequences of this highly lignin-depolymerizing strain revealed that the genome lacked any of the well-known dye-decolorizing peroxidase or catalase-peroxidase that are commonly reported to be involved in lignin depolymerization by bacteria, indicating that strain S11Y has distinct sets of potential lignin depolymerization genes. The oxidative stress-related enzymes Cu/Zn type-superoxide dismutase (Sod2) and a heme-containing monofunctional catalase (Kat2) were identified in the genome sequences that are of interest. Their lignin-depolymerizing ability were evaluated by treating Alkali lignin (AL) with each enzyme and their degradation ability were evaluated using gel-permeation chromatography (GPC), ultrahigh-pressure liquid chromatography-mass spectrometry (UHPLC/MS), and gas chromatography-mass spectrometry (GC/MS), which successfully proved lignin depolymerizing ability. Successful evaluation of lignin depolymerizing enzymes can be applicable for lignin pretreatment process in green energy production and generation of valuable chemicals in bio-refinery.

Application of Box-Behnken design to mineralization and color removal of palm oil mill effluent by electrocoagulation process.

In this study, palm oil mill effluent (POME) was treated using electrocoagulation, whereby the influencing factors including voltage, electrolysis time, and electrolyte amount were optimized to achieve the highest chemical oxygen demand (COD) and color removal efficiencies. Graphite was selected as electrode material due to its performance better compared to aluminum and copper. Response surface methodology (RSM) was carried out for optimization of the electrocoagulation operating parameters. The best model obtained using Box-Behnken design (BBD) were quadratic for COD removal (R2 = 0.9844), color reduction (R2 = 0.9412), and oil and grease removal (R2 = 0.9724). The result from the analysis of variance (ANOVA) was obtained to determine the relationship between factors and treatment efficiencies. The experimental results under optimized conditions such as voltage 14, electrolysis time of 3 h, and electrolyte amount of 13.41 g/L show that the electrocoagulation process effectively reduced the COD (56%), color (65%), and oil and grease (99%) of the POME treatment. Graphical abstract.

Electrochemical oxidation of palm oil mill effluent using platinum as anode: Optimization using response surface methodology.

This work investigates the electrochemical oxidation of palm oil mill effluent (POME) treatment using platinum (Pt) as anode and graphite as a cathode. The response surface methodology was used to investigate the relationships between different factors conditions (voltage, electrolysis time and chemical support) and responses of the treatment (chemical oxygen demand reduction, colour removal, and total oil removal). A quadratic mathematical model was chosen for all responses using Box-Behnken Design (BBD) with R2 0.9853 for COD reduction, R2 0.9478 for colour removal and R2 0.9185 for total oil removal. According to Derringer's function desirability, under the optimum condition (Voltage 15, electrolysis time 2 h, and 19.95 mg/L NaCl) of POME treatment, 84% of COD reduction, 98% of colour removal and 99% total oil of removal could be achieved. These results indicate that platinum as an anode material is effective for the electrochemical oxidation treatment of POME.

Draft Genome Sequences of Three Nitrogen-Fixing Strains Isolated from Soil Cooled for Growing Temperate Root Crops in a Tropical Climate.

Nitrogen-fixing bacteria can form a symbiotic relationship with several members of the major plant groups and with fungi. Here, we present the draft genome sequences of three nitrogen-fixing strains isolated from soil cooled for growing temperate root crops in a tropical climate.

Future trends and patterns in leachate biological treatment research from a bibliometric perspective.

Leachate has become a great deal of concern due to its complex properties which are primarily caused by the high concentrations of organics and ammonia. Thus, proper leachate treatment is required prior to its discharge. Leachate can be treated in various ways, and biological treatment is one of the approaches. This treatment has been shown to be both effective and cost-efficient while offering the possibility of resource recovery in the form of bioenergy. In this study, the underlying patterns in publications related to leachate biological treatment were uncovered through bibliometric analysis. This study also lays the groundwork for a deeper understanding of the past, current, and future trends of the leachate biological treatment. Research publications from 1974 to 2021 were retrieved from the Scopus database, and it was identified that 2013 articles were published in the span of 47 years. From the analyzed publications, China played a leading role in publishing leachate biological treatment research articles as well as having the most productive institutions and authors. Meanwhile, the USA was found to be the most active country in initiating international collaborations with 33 countries. The research hotspots were also successfully identified using keyword co-occurrences analysis. Anaerobic digestion and constructed wetland were revealed to be the research hotspots. The critical role of biological treatment in removing nitrogen from leachate was also highlighted. Besides, numerous research gaps were identified in the application of aerobic granular sludge (AGS) for leachate treatment. This can be a potential area for research in the future. Finally, future research should be encouraged to focus on the use of sustainable treatment systems in which energy recovery in the form of biogases is promoted.

Draft Genome Sequence of Lignin-Degrading Agrobacterium sp. Strain S2, Isolated from a Decaying Oil Palm Empty Fruit Bunch.

We report the draft genome sequence of Agrobacterium sp. strain S2, isolated from a decaying oil palm empty fruit bunch (OPEFB) in Negeri Sembilan, Malaysia, which yields potential genes encoding lignin degradation enzymes. This genome of 9,722,071 bp exhibited 58.9% GC content, 10,416 coding genes, and 12 RNAs.

Enzymatic and genetic characterization of lignin depolymerization by Streptomyces sp. S6 isolated from a tropical environment.

The conversion of lignocellulosic biomass into bioethanol or biochemical products requires a crucial pretreatment process to breakdown the recalcitrant lignin structure. This research focuses on the isolation and characterization of a lignin-degrading bacterial strain from a decaying oil palm empty fruit bunch (OPEFB). The isolated strain, identified as Streptomyces sp. S6, grew in a minimal medium with Kraft lignin (KL) as the sole carbon source. Several known ligninolytic enzyme assays were performed, and lignin peroxidase (LiP), laccase (Lac), dye-decolorizing peroxidase (DyP) and aryl-alcohol oxidase (AAO) activities were detected. A 55.3% reduction in the molecular weight (Mw) of KL was observed after 7 days of incubation with Streptomyces sp. S6 based on gel-permeation chromatography (GPC). Gas chromatography-mass spectrometry (GC-MS) also successfully highlighted the production of lignin-derived aromatic compounds, such as 3-methyl-butanoic acid, guaiacol derivatives, and 4,6-dimethyl-dodecane, after treatment of KL with strain S6. Finally, draft genome analysis of Streptomyces sp. S6 also revealed the presence of strong lignin degradation machinery and identified various candidate genes responsible for lignin depolymerization, as well as for the mineralization of the lower molecular weight compounds, confirming the lignin degradation capability of the bacterial strain.

Complete Genome Sequence of Lignin-Degrading Streptomyces sp. Strain S6, Isolated from an Oil Palm Plantation in Malaysia.

Streptomyces spp. are bacteria that are responsible for the degradation of aromatic compounds and produce secondary metabolites. Here, we present a complete genome sequence of Streptomyces sp. strain S6, which was isolated from an oil palm plantation, with a 7.8-Mbp liner chromosome, a GC content of 72%, and 4,266 coding sequences.

Optimization of thermostable organic solvent-tolerant lipase production by thermotolerant Rhizopus sp. using solid-state fermentation of palm kernel cake.

This study enhanced the production of thermostable organic solvent-tolerant (TS-OST) lipase by locally isolated thermotolerant Rhizopus sp. strain using solid-state fermentation (SSF) of palm kernel cake (PKC). The optimum conditions were achieved using a series of statistical approaches. The cultivation parameters, which include fermentation time, moisture content, temperature, pH, inoculum size, various carbon and nitrogen sources, as well as other supplements, were initially screened by the definitive screening design, and one-factor-at-a-time using PKC as the basal medium. Three significant factors (olive oil concentration, pH, and inoculum size) were further optimized using face-centred central composite design. The results indicated a successful and significant improvement of lipase activity by almost two-fold compared to the initial screening production. The findings showed that the optimal conditions were 2% (v/w) inoculum size, 2% (v/w) olive oil, 0.6% (w/w) peptone, 2% (v/w) ethanol, 70% moisture content at initial pH 10.0 and 45 °C within 72 h of fermentation. Process optimization resulted in maximum lipase activity of 58.63 U/gram dry solids (gds). The analysis of variance showed that the statistical model was significant (p value <0.0001) and reliable with a high value of R2 (0.98) and adjusted R2 (0.96). This indicates a better correlation between the actual and predicted responses of lipase production. By considering this study, the low-cost PKC through SSF appears to be promising in the utilization of agro-industrial waste for TS-OST lipase production. This is because satisfactory enzyme activity could be attained that promises industrial applications.