Exploring the antioxidant potential of lignin isolated from black liquor of oil palm waste

This study was conducted to evaluate the potential antioxidant activity of lignin obtained from black liquor, a hazardous waste product generated during the extraction of palm oil. Antioxidant potential of the extracted lignin was evaluated by dissolving the extracted samples in 2 different solvent systems, namely, 2-methoxy ethanol and DMSO. Results revealed high percent inhibition of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical in the lignin sample dissolved in 2-methoxy ethanol over DMSO (concentration range of 1–100 μg/ml). Lignin extracted in 2-methoxy ethanol exhibited higher inhibition percentage (at 50 μg/ml, 84.2%), whereas a concentration of 100 μg/ml was found to be effective in the case of the DMSO solvent (69.8%). Fourier transform infrared (FTIR) spectrometry revealed that the functional groups from the extracted lignin and commercial lignin were highly similar, indicating the purity of the lignin extracted from black liquor. These results provide a strong basis for further applications of lignin in the food industry and also illustrate an eco-friendly approach to utilize oil palm black liquor. To cite this article: R. Bhat et al., C. R. Biologies 332 (2009).     

Life cycle assessment of kraft lignin for polymer applications

Purpose

Lignin is a by-product of wood pulping that is normally used as fuel on-site (black liquor), but also has some applications in the field of new biomaterials. This study focuses on the life cycle inventory of lignin originating from the kraft pulping process, for polymer applications. The system boundary includes lignin precipitation from black liquor, washing, and drying, but excludes subsequent application-specific compatibilization modifications. Lignin transportation is considered to rely exclusively on trucking.

Methods

This work is based on the ecoinvent v2.2 database and the IMPACT 2002+ impact assessment method. Special attention is given to the net effect of lignin precipitation on the mass and energy balances of the kraft process. Because the kraft black liquor supply will far exceed the demand for non-fuel uses for the foreseeable future, it is considered appropriate to use either the marginal variation method of physical allocation or a system boundary expansion. Consequently, the system boundary includes natural gas as a substitute fuel (when applicable) but excludes wood harvesting and the pulping process.

Results and discussion

The main impacts of kraft lignin come from the natural gas subsystem (fuel substitution and drying) despite a significantly cleaner combustion than for black liquor. Other significant contributors include the production of carbon dioxide for precipitation, sulfuric acid for washing, and sodium hydroxide to make up for sodium losses, all of which have some improvement potential.

Conclusions

The environmental profile of kraft lignin tends to be preferable to synthetic organic compounds of similar molecular complexity because its initial transformation chain is relatively energy efficient. It is thus an environmentally sound choice for polymer applications as long as near-unity substitution ratios can be achieved without requiring compatibilization modifications that are too environmentally intensive and without affecting other stages of the product life cycle. In particular, the end-of-life performance depends on long-term lignin sequestration.     

Phyto-availability and speciation change of heavy metals in soils amended with lignin as micro-fertilizer

Lignin is a primary byproduct from the black liquor treatment in paper making industries, its application as micro-fertilizer in agricultural land might provide a promising alternative to sewage discharge. However, application of such a micro-fertilizer might affect the soil properties and result in soil pollution. In this study, the effects of lignin application on phytoavailability and speciation change of heavy metals in soils were investigated. Greenhouse experiments showed that lignin application improved the growth of winter wheat (Triticum aestivum L.) in all three soils investigated. The increase of the biomass for wheat shoot was 59.7%, 39.8% and 12.3% for Beijing soil, Jiangxi soil and Dongbei soil, respectively. In contrast, lignin amendment decreased the concentrations of heavy metals in wheat shoots from 2.2% to 61.0%. Sequential extraction procedure of a three-step BCR was used to investigate the fraction distribution. The extractable fractions were specified as fraction B1: water soluble, exchangeable and carbonate bound or weakly specifically adsorbed; B2: Fe-Mn oxide bound; B3: organic matter and sulfide bound. The results showed that lignin application led to the redistribution of heavy metals in each fraction. Generally, heavy metals decreased in B1 and B2 fractions and increased in B3 fraction. Upon the results short-term application of lignin in agricultural land not only improves the growth of wheat but also reduces the phyto-abailability of heavy metal in wheat.     

Phyto-availability and speciation change of heavy metals in soils amended with lignin as micro-fertilizer

Lignin is a primary byproduct from the black liquor treatment in paper making industries, its application as micro-fertilizer in agricultural land might provide a promising alternative to sewage discharge. However, application of such a micro-fertilizer might affect the soil properties and result in soil pollution. In this study, the effects of lignin application on phyto-availability and speciation change of heavy metals in soils were investigated. Greenhouse experiments showed that lignin application improved the growth of winter wheat (Triticum aestivum L.) in all three soils investigated. The increase of the biomass for wheat shoot was 59.7%, 39.8% and 12.3% for Beijing soil, Jiangxi soil and Dongbei soil, respectively. In contrast, lignin amendment decreased the concentrations of heavy metals in wheat shoots from 2.2% to 61.0%. Sequential extraction procedure of a three-step BCR was used to investigate the fraction distribution. The extractable fractions were specified as fraction B1: water soluble,     

添加玉米和水稻秸秆对淹水土壤pH、二氧化碳及交换态铵的影响

通过温室土壤培养试验,研究了不同添加量玉米和水稻秸秆对淹水土壤pH、CO₂及交换态铵的影响.结果表明：在接近中性的土壤中加入秸秆可使土壤pH值降低,4 g·kg^-1玉米和水稻秸秆处理的土壤pH值均与对照差异显著（P＜0.05）,而1 g·kg^-1玉米和水稻秸秆处理与对照差异不显著（P＞0.05）.土壤溶液中的CO₂含量随秸秆添加量的增加而增大,1 g·kg^-1玉米和水稻秸秆处理的土壤溶液CO₂含量最大值分别为35.9％和31.9％（v/v）,与对照（25.8％）差异达显著水平（P＜0.05）,但两者间差异不显著（P＞0.05）;4 g·kg^-1玉米和水稻秸秆处理的土壤溶液CO₂含量最大值分别为54.2％和41.8％（v/v）,与对照差异极显著（P＜0.01）,两者间差异也达显著水平（P＜0.05）.在不施氮肥的情况下,添加秸秆可降低土壤铵态氮浓度,且铵态氮浓度随秸秆添加量的增加而降低,不同添加量处理间差异显著（P＜0.05）;在施入氮肥的情况下,1 g·kg^-1玉米和水稻秸秆处理提高了土壤铵态氮浓度,而4 g·kg^-1玉米和水稻秸秆处理降低了土壤铵态氮浓度.无论是否施入氮肥,玉米和水稻秸秆处理的土壤铵态氮浓度差异不显著（P＞0.05）.     

Phyto-availability and speciation change of heavy metals in soils amended with lignin as micro-fertilizer

Lignin is a primary byproduct from the black liquor treatment in paper making industries, its application as micro-fertilizer in agricultural land might provide a promising alternative to sewage discharge. However, application of such a micro-fertilizer might affect the soil properties and result in soil pollution. In this study, the effects of lignin application on phytoavailability and speciation change of heavy metals in soils were investigated. Greenhouse experiments showed that lignin application improved the growth of winter wheat (Triticum aestivum L.) in all three soils investigated. The increase of the biomass for wheat shoot was 59.7%, 39.8% and 12.3% for Beijing soil, Jiangxi soil and Dongbei soil, respectively. In contrast, lignin amendment decreased the concentrations of heavy metals in wheat shoots from 2.2% to 61.0%. Sequential extraction procedure of a three-step BCR was used to investigate the fraction distribution. The extractable fractions were specified as fraction B1: water soluble, exchangeable and carbonate bound or weakly specifically adsorbed; B2: Fe-Mn oxide bound; B3: organic matter and sulfide bound. The results showed that lignin application led to the redistribution of heavy metals in each fraction. Generally, heavy metals decreased in B1 and B2 fractions and increased in B3 fraction. Upon the results short-term application of lignin in agricultural land not only improves the growth of wheat but also reduces the phyto-abailability of heavy metal in wheat.     

淹水条件下添加有机物料对蔬菜地土壤硝态氮及氮素气体排放的影响

蔬菜地大量施用氮肥可以引起土壤硝态氮积累,导致土壤退化,快速消除土壤积累的硝态氮,可以提高蔬菜地土壤质量,延长其使用时间.在硝态氮(360 mg N·kg^-1)积累的蔬菜地土壤中,分别加入0、2500、5000和7500 kg C·hm^-2黑麦草(记为CK、C₂₅₀₀、C₅₀₀₀和C₇₅₀₀),淹水条件下,30 ℃恒温室内培养240 h,研究土壤硝态氮含量及氮素气体排放量变化.结果表明：培养结束时,CK处理中土壤硝态氮含量高达310 mg N·kg^-1,添加黑麦草能有效地消除土壤中积累的硝态氮,C₂₅₀₀、C₅₀₀₀和C₇₅₀₀处理中土壤硝态氮含量降低至10 mg N·kg^-1以下需要的时间分别为240、48和24 h.添加黑麦草显著提高了土壤pH,降低了土壤电导率,其变化幅度随黑麦草添加量的增加而增大.添加黑麦草处理的土壤N₂O和N₂累积排放量为270～378 mg N·kg^-1,N₂O/N₂为0.6～1.5.淹水条件下添加黑麦草可快速消除蔬菜地土壤积累的硝态氮,但应充分重视N₂O在这一过程中的大量排放.     

蚯蚓活动对红壤磷素主要形态及有效磷含量的影响

通过盆钵生物试验和采用Hedley磷素分级方法研究了秉氏环毛蚓(Pheretima pingi)对红壤磷素主要形态和红壤有效磷含量的影晌.结果表明,在蚯蚓和有机物料(稻草、花生秸、油菜秸)的共同作用下,经过100d培养后土壤有效磷含量显著提高.统计分析结果表明,花生秸接种蚯蚓处理与不接种蚯蚓处理和油莱秸接种蚯蚓处理与不接种蚯蚓处理之间的土壤有效磷含量差异均达显著水平.采用Hedley磷素分级法测得的树脂磷由原土的痕量增加到10.5～17.8 mg·kg^-1,NaHCO₃溶解态磷由原土的14.5 mg·kg^-1增加到23.5～53.6 mg·kg^-1,微生物细胞磷由原土的1.0 mg·kg^-1增加到6.8～9.7 mg·kg^-1,土壤有机磷含量由原土的37.9 mg·kg^-1增加到50.7～59.3 mg·kg^-1,而土壤中活性最低的残留磷含量则有所降低.蚯蚓活动对红壤磷素具有较强的活化作用.     

Methods for Facilitating Microbial Growth on Pulp Mill Waste Streams and Characterization of the Biodegradation Potential of Cultured Microbes

The kraft process is applied to wood chips for separation of lignin from the polysaccharides within lignocellulose for pulp that will produce a high quality paper. Black liquor is a pulping waste generated by the kraft process that has potential for downstream bioconversion. However, the recalcitrant nature of the lignocellulose resources, its chemical derivatives that constitute the majority of available organic carbon within black liquor, and its basic pH present challenges to microbial biodegradation of this waste material. Methods for the collection and modification of black liquor for microbial growth are aimed at utilization of this pulp waste to convert the lignin, organic acids, and polysaccharide degradation byproducts into valuable chemicals. The lignocellulose extraction techniques presented provide a reproducible method for preparation of lignocellulose growth substrates for understanding metabolic capacities of cultured microorganisms. Use of gas chromatography-mass spectrometry enables the identification and quantification of the fermentation products resulting from the growth of microorganisms on pulping waste. These methods when used together can facilitate the determination of the metabolic activity of microorganisms with potential to produce fermentation products that would provide greater value to the pulping system and reduce effluent waste, thereby increasing potential paper milling profits and offering additional uses for black liquor.     

Lignin characteristics in soil profiles in different plant communities in a subtropical mixed forest

Aims Lignin is generally considered as an important indicator of soil organic carbon (SOC) storage and dynamics. To evaluate the effects of plant communities and soil depth on soil lignin is critical to better understand forest carbon cycling.Methods We compared lignin content and chemical signature in three soil depths of four major plant communities in a subtropical forest, which located in the north part of Wuling Mountains, China. Lignin was measured using CuO oxidation method.Important findings Both lignin content and its biochemical signature in plant litter varied among communities. However, these differences were mostly no longer exist in the upper soil layers. Lignin chemistry in soils inherited some of the biochemical signature of lignin in litter, but in a diminished magnitude. These results suggest that different plant communities had similar decomposition process with varying rates, caused diminished differences in lignin content and its biochemical signature. Lignin content decreased with soil depth, but the biochemical signature of lignin was not significantly different among soil layers for all communities, which suggests that vertical movement of lignin within the soil profile is very likely a key process causing this similar biochemical signature. These results emphasized the important roles of lignin inputs and soil eluviation in shaping lignin characteristics and distribution in forest soils, which pinpoint the urgent need to consider hydrological processes in studying forest soil carbon cycling.     

Laccase-mediated synthesis of lignin-core hyperbranched copolymers

Lignin, one of the major chemical constituents of woody biomass, is the second most abundant biopolymer found in nature. The pulp and paper industry has long produced lignin on the scale of millions of tons annually as a by-product of the pulping process, and the dawn of cellulosic ethanol production has further contributed to this amount. Historically, lignin has been perceived as a waste material and burned as a fuel for the pulping process. However, recent research has been geared toward developing cost-effective technologies to convert lignin into valuable commodities. Attributing to the polyphenolic structure of lignin, enzymatic modification of its surface using laccases (benzenediol:oxygen oxidoreductases, EC 1.10.3.2) has demonstrated to be highly successful. The current study aims at developing lignin-core hyperbranched copolymers via the laccase-assisted copolymerization of kraft lignin with methylhydroquinone and a trithiol. Based on the physical properties of the resulting material, it is likely that crosslinking reactions have taken place during the drying process to produce a copolymeric network rather than discrete hyperbranched copolymers, with NMR data providing evidence of covalent bonding between monomers. Preliminary thermal analysis data reveals that the copolymeric material possesses a moderate glass transition temperature and exhibits good thermostability, thus may have potential application as a lignin-based thermoplastic. Scanning electron microscopy images confirm the smooth, glossy surface of the material and that it is densely packed. The presented results are a sustainable, ecofriendly, economic method to create an exciting novel biomaterial from a renewable feedstock while further enhancing lignin valorization.     

Structural analysis of alfa grass (Stipa tenacissima L.) lignin obtained by acetic acid/formic acid delignification

Alfa grass lignin obtained by the acetic acid/formic acid/water CIMV pulping process was characterized by FTIR and (1)H, (13)C-(1)H 2D HSQC, and (31)P NMR spectroscopies. Lignin samples purified by further dissolution/precipitation or basic hydrolysis steps were also analyzed. The CIMV alfa lignin is a mixture of low molar mass compounds (M(n) = 1500 g/mol) of SGH type with β-O-4 ether bonds as the major interunit linkage. The crude lignin contains fatty acids and residual polysaccharides. It also contains large amounts of acetate and hydroxycinnamates, mostly in the γ-position of β-O-4 interunit linkages. Although partial acetylation induced by the process cannot be excluded, the absence of aromatic acetates and acetylated polysaccharides in crude lignin demonstrates the mildness of the process. By combining smooth alkaline hydrolysis and dissolution/precipitation steps to the CIMV pulping, it is possible to produce a purified lignin with a composition and a structure quite analogous to that of the native polymer in the plant.     

Bacterial decolorization of black liquor in axenic and mixed condition and characterization of metabolites

The pulping byproducts (black liquor) cause serious environmental problem due to its high pollution load. In order to search the degradability of black liquor, the potential bacterial strains Citrobacter freundii (FJ581026) and Citrobacter sp. (FJ581023) were applied in axenic and mixed condition. Results revealed that the mixed bacterial culture are more effective than axenic condition and can reduce 82% COD, 79% AOX, 79% color and 60% lignin after 144 h of incubation period. Additionally, the optimum activity of lignin degrading enzyme was noted at 96 h and characterized as manganese peroxidase (MnP) by SDS–PAGE analysis. Further, the HPLC analysis of control and bacterial degraded sample has shown the reduction as well as shifting of peaks compared to control indicating the degradation as well as transformation of compounds of black liquor. The comparative GC–MS analysis of control and degraded black liquor revealed that along with lignin fragment some chlorophenolic compounds 2,4,6-trichlorophenol, 2,3,4,5-tetrachlorophenol and pentachlorophenol were detected in black liquor degraded by axenic culture whereas these chlorophenolic compounds were completely absent in black liquor degraded by mixed bacterial culture. These chlorophenol inhibit the oxidative degradation which seems a major reason behind the low degradability of axenic degradation compared to mixed culture. The innovation of this aerobic treatment of alkaline black liquor opens additional possibilities for the better treatment of black liquor along with its metabolic product.     

Microbial community structure in soils with decomposing residues from plants with genetic modifications to lignin biosynthesis

Lignin is a major determinant of the decomposition of plant materials in soils. Advances in transgenic technology have led to the possibility of modifying lignin to improve the pulping properties of plant materials for papermaking. Previous studies have shown that lignin modifications also affect the rate of plant material decay in soil. The aim of this work was to investigate short-term changes in soil microbial community structures when tobacco residues with reduced activity of enzymes in the monolignol pathway decompose. The residues from lignin-modified plants all decomposed faster than unmodified plant materials. The relative proportions of some of the structural groups of microbial phospholipid fatty acids were affected by genetic modifications, especially the proportion of double unsaturated chain fatty acids, indicative of fungi.     

Microbial decomposition of synthetic C-labeled lignins in nature: lignin biodegradation in a variety of natural materials

Lignin biodegradation in a variety of natural materials was examined using specifically labeled synthetic C-lignins. Natural materials included soils, sediments, silage, steer bedding, and rumen contents. Both aerobic and anaerobic incubations were used. No C-labeled lignin biodegradation to labeled gaseous products under anaerobic conditions was observed. Aerobic C-labeled lignin mineralization varied with respect to type of natural material used, site, soil type and horizon, and temperature. The greatest observed degradation occurred in a soil from Yellowstone National Park and amounted to over 42% conversion of total radioactivity to CO(2) during 78 days of incubation. Amounts of C-labeled lignin mineralization in Wisconsin soils and sediments were significantly correlated with organic carbon, organic nitrogen, nitrate nitrogen, exchangeable calcium, and exchangeable potassium.     

Biopulping of wood chips with Phlebia brevispora BAFC 633 reduces lignin content and improves pulp quality

The white-rot fungus Phlebia brevispora BAFC 633 produces laccases in large proportions. In this work P. brevispora BAFC 633 was grown on Pinus taeda wood chips in 10-L bioreactors. To select the biopulping experimental conditions, we analyzed the variables affecting enzymatic laccase activity in the culture supernatants, indicating that the suitable incubation temperature was 30 °C in order to promote enzyme stability. Phlebia brevispora BAFC 633 secreted 744 U/g of laccase, selectively removing lignin during biotreatment of wood chips, causing a reduction in Kappa number and 10% weight loss, and creating a more open structure and better access to the pulping liquor, which would require less chemical consumption, thus diminishing the environmental impact of the chemical pulping process.These results support the biotechnological potential of P. brevispora BAFC 633 for biopulping processes and enhance the potential for bioprospecting native isolates of the microflora of our country's natural environment.     

Influence of Pb contamination in boreal forest soil on the growth and ligninolytic activity of litter-decomposing fungi

Lignin mineralization activity of three basidiomycetous litter-decomposing fungi (LDF) was studied with humus layer samples taken from a boreal forest soil. The total Pb concentration in the samples was 32,000 mg kg(-1) and water soluble Pb 67 mg kg(-1). Synthetic lignin mineralization by Collybia dryophila and Clitocybe (Lepista) nebularis was strongly inhibited, whereas Stropharia coronilla was more tolerant to Pb stress in soil and liquid cultures. Purified laccases maintained their activity and purified MnPs remained partly active up to a concentration of 1450 mg Pb l(-1). High concentrations of Pb inhibited the growth of LDF and affected the activity of ligninolytic enzymes, but the extent of inhibition varied among different LDF species. In consequence, Pb contamination in soil may have a negative impact on recycling of organic carbon.     

Short-term effects on soil properties and wheat production from secondary paper sludge application on two Mediterranean agricultural soils

This study was conducted under greenhouse conditions to evaluate the potential use of SPS as a fertilizer, amendment and/or liming agent for wheat (Triticum aestivum L.). Two representative Mediterranean agricultural soils, a Cambic Arenosol (cmAR) and a Cromic Cambisol (crCM) were used. Treatments included four sludge rates ranging from 0 to 40 g kg(-1) (equivalent of 0, 38, 88 and 120 Mg ha(-1)). A significant increment in soil pH, organic carbon, N total, available P and exchangeable K were observed in both soils. Sludge application significantly increased N and decreased Zn, Mn and Cu concentrations in wheat. Wheat grain yields were reduced by 33% and 37% when 120 Mg SPS ha(-1) was applied to cmAR and crCM soils, respectively, due apparently to unavailability of Mg. However, straw yields, with much lower Mg requirements, increased significantly with SPS rates. Secondary pulp mill sludge seems to be a potential source of organic matter, N, P, K and a potential soil amendment liming agent for acid soils, when appropriate supplemental fertilizer was provided. For grain crops grown in these soils, addition of Mg is required for proper nutrient balance.     

Inhibitory effect of lignin by-products of pulping on yeast growth

The antimicrobial properties of lignin by-products obtained by organic solvent, neutral sulfite semichemical and kraft pulping were shown in a series of yeasts. Lignin can act as an inhibitor of growth ofSporobolomyces roseus, Candida tropicalis, Trichosporon cutaneum andCandida albicans. Oxidation of all lignin samples tested depresses their inhibitory effects.     

Fractionation of wheat straw by atmospheric acetic acid process

Fractionation of wheat straw was investigated using an atmospheric acetic acid process. Under the typical conditions of 90% (v/v) aqueous AcOH, 4% H(2)SO(4) (w/w, on straw), ratio of liquor to straw (L/S) 10 (v/w), pulping temperature 105 degrees C, and pulping time 3h, wheat straw was fractionated to pulp (cellulose), lignin and monosaccharides mainly from hemicellulose with yields of approximately 50%, 15% and 35%, respectively. Acetic acid pulp from the straw had an acceptable strength for paper and could be bleached to a high brightness over 85% with a short bleaching sequence. Acetic acid pulp was also a potential feedstock for fuels and chemicals. The acetic acid process separated pentose and hexose in wheat straw to a large extent. Most of the pentose (xylan) was dissolved, whereas the hexose (glucan) remained in the pulp. Approximately 30% of carbohydrates in wheat straw were hydrolyzed to monosaccharides during acetic acid pulping, of which xylose accounted for 70% and glucose for 12%. The acetic acid lignin from wheat straw showed relatively lower molecular weight and fusibility, which made the lignin a promising raw material for many products, such as adhesive and molded products.