Hydrolysis Of Wood Research Articles

Engineering Rhodosporidium toruloides for sustainable production of value-added punicic acid from glucose and wood residues

Rhodosporidium toruloides has emerged as a prominent candidate for producing single-cell oil from cost-effective feedstocks. In this study, the capability of R. toruloides to produce punicic acid (PuA), a representative plant unusual fatty acid, was investigated. The introduction of acyl lipid desaturase and conjugase (PgFADX) allowed R. toruloides to accumulate 3.7 % of total fatty acids as PuA. Delta-12 acyl lipid desaturase (PgFAD2) and diacylglycerol acyltransferase 2 were shown to benefit PuA production. The strain with PgFADX and PgFAD2 coexpression accumulated 12 % of its lipids as PuA from glucose, which translated into a PuA titer of 451.6 mg/L in shake flask condition. Utilizing wood hydrolysate as the feedstock, this strain produced 6.4 % PuA with a titer of 310 mg/L. Taken together, the results demonstrated that R. toruloides could serve as an ideal platform for the production of plant-derived high-value conjugated fatty acid using agricultural and forestry waste as feedstock.

Integrated biorefinery approach for utilization of wood waste into levulinic acid and 2-Phenylethanol production under mild treatment conditions

In a bid to explore the on-site biorefinery approach for conversion of forestry residues, lignocellulosic biomass into value-added products was studied. The bark white pine wood was subjected to the microwave technique of fast and slow hydrolysis under varying acid and biomass concentrations to produce levulinic acid (LA). The HCl (2% v/v) and plant biomass (1% w/v) were identified as the optimum conditions for fast wood hydrolysis (270 ºC for 12 sec), which led to maximum LA yield of 446.68 g/kgPB. The proposed sustainable approach is mild, quick, and utilized a very low concentration of the HCl for the production of LA. The hydrolysate was used as a medium for Kluyveromyces marxianus growth to produce 2-phenylethanol (2-PE). K. marxianus used 74–95% of furfural from hydrolysate as a co-substrate to grow. The proposed model of the integrated biorefinery is an affordable on-site approach of using forest waste into localized solutions to produce LA and 2-PE.

Improved reducing sugars production from enzymatic hydrolysis of rubber wood by surfactant-assisted hydrothermal pretreatment

In this work, a facile and environmentally friendly strategy was proposed for the production of reducing sugars from enzymatic hydrolysis of rubber wood by surfactant-assisted hydrothermal pretreatment. Compared with hydrothermal pretreatment, the addition of surfactants (Tween 40) significantly increased the reducing sugars concentration, the highest reducing sugars concentration was up to 22.47 g/L. After surfactant-assisted pretreatment, the crystallinity index of rubber wood hydrolysis residues increased and then decreased with the addition amount of Tween 40. The surfactant-assisted pretreated rubber wood featured high cellulose and hemicellulose conversion rates of 95.1% and 95.4% respectively, which was 122.2% and 41.1% higher than the hydrothermally pretreated rubber wood. It was also found that surfactant-assisted hydrothermal pretreatment had the same improvement effect on increasing the sugar production of other lignocellulose. The results showed that surfactant-assisted hydrothermal pretreatment is a promising and universal method for developing biomass-based products.

Environmental assessment of Rhodosporidium toruloides-1588 based oil production using wood hydrolysate and crude glycerol

Rhodosporidium toruloides, an oleaginous yeast, is a potential feedstock for biodiesel production due to its ability to utilize lignocellulosic biomass-derived hydrolysate with a considerably high lipid titer of 50–70 % w/w. Hence, for the first-time environmental assessment of large-scale R. toruloides-based biodiesel production from wood hydrolysate and crude glycerol was conducted. The global warming potential was observed to be 0.67 kg CO2 eq./MJ along with terrestrial ecotoxicity of 1.37 kg 1,4-DCB eq./MJ and fossil depletion of 0.13 kg oil eq./MJ. The highest impacts for global warming (∼45 %) and fossil depletion (∼37 %) are attributed to the use of chloroform for lipid extraction while fuel consumption for transportation contributed more than 50 % to terrestrial ecotoxicity. Further, sensitivity analysis revealed that maximizing biodiesel yield by increasing lipid yield and solid loading could contribute to reduced environmental impacts. In nutshell, this investigation reveals that environmental impact varies with the type of chemical utilized.

Impact of a conditioning step during the treatment of wood with melamine-formaldehyde resin on dimensional stabilisation

Abstract The dimensional stabilisation of wood using thermosetting resins relies on the resin uptake into the cell walls. This study tested if a conditioning step after the impregnation and before the final heat-curing enhances the cell wall uptake to improve dimensional stabilisation without increasing the chemical consumption. Small blocks of Scots pine sapwood were vacuum-impregnated with an aqueous melamine formaldehyde solution and conditioned at 33, 70, or 95 % RH for up to 1 week before drying and curing the blocks at 103 °C. However, the conditioning step decreased the cell wall bulking and the moisture exclusion effect compared to the immediate heat curing of the impregnated samples. Analyses of the resin-treated samples by scanning electron microscopy, IR spectroscopy and confocal Raman microspectroscopy provided evidence of wood hydrolysis and polycondensation of the resin within the cell lumen during the conditioning step. Hydrolysis and removal of wood constituents may have counterbalanced the cell wall bulking of the resin. Polycondensation of the resin in the lumen increased its molecule size, which could have hindered the cell wall diffusion of the resin.

Metabolic engineering of Paenibacillus polymyxa for effective production of 2,3-butanediol from poplar hydrolysate

2,3-Butanediol is an essential renewable fuel. The synthesis of 2,3-butanediol using Paenibacillus polymyxa has attracted increasing attention. In this study, the glucose-derived 2,3-butanediol pathway and its related genes were identified in P. polymyxa using combined transcriptome and metabolome analyses. The functions of two distinct genes ldh1 and ldh3 encoding lactate dehydrogenase, the gene bdh encoding butanediol dehydrogenase, and the spore-forming genes spo0A and spoIIE were studied and directly knocked out or overexpressed in the genome sequence to improve the production of 2,3-butanediol. A raw hydrolysate of poplar wood containing 27 g/L glucose and 15 g/L xylose was used to produce 2,3-butanediol with a maximum yield of 0.465 g/g and 93 % of the maximum theoretical value, and the total production of 2,3-butanediol and ethanol reached 21.7 g/L. This study provides a new scheme for engineered P. polymyxa to produce renewable fuels using raw poplar wood hydrolysates.

PSIII-4 Effect of Two Torula Yeast Sources on Growth Performance, Intestinal Health, and Immune Function of Weanling Pigs

Abstract An experiment was conducted to test the hypothesis that dietary inclusion of either a conventional or a novel source of torula yeast in diets for weanling pigs improves growth performance and intestinal health. The novel torula yeast was produced using forestry byproducts (i.e., wood hydrolysate) as the carbon source, whereas the conventional torula yeast was produced using wheat dextrose as the carbon source. A total of 120 weanling pigs (6.53 ± 0.78 kg) were allotted to three treatments with four pigs per pen and ten replicate pens per diet. Pigs were fed one of three diets from d 1 to 14 post-weaning (phase 1), whereas all pigs were fed a common diet in phase 2 (d 15 to 28). The three dietary treatments included a control diet that contained 5% fishmeal, 3.5% plasma protein, and no torula yeast. The second diet contained 1.5% fishmeal, 14% of the novel torula yeast, and no plasma protein, whereas the third diet contained 1.5% fishmeal, 14% of the conventional torula yeast, and no plasma protein. Pig weights were recorded on d 1, d 14, and d 28. Feed allotments were recorded daily, and feed left in the feeders was recorded on d 14 and 28 to calculate average daily gain, average daily feed intake, and average gain to feed ratio. Fecal scores were visually assessed every other day. On d 7, one pig per pen was euthanized to collect ileal tissue for assessment of morphology. At the end of phases 1 and 2, blood samples were collected, and cytokines, plasma urea nitrogen, peptide YY, immunoglobulin G, total protein, and albumin were analyzed. Data were analyzed using an ANOVA in the Mixed Procedure of SAS with pen as the experimental unit. Diet was the fixed effect, whereas weaning weight was the random effect. Results indicated that both sources of torula yeast could replace fish meal and plasma protein without negatively affecting overall growth performance, intestinal morphology, or blood characteristics of pigs (Table 1). Pigs fed one of the diets containing torula yeast had reduced (P < 0.05) fecal scores during phase 1 compared with pigs fed the control diet. On d 14, pigs fed the conventional torula yeast diet had greater (P < 0.05) concentration of interleukin-2 in plasma compared with pigs fed the control diet. Greater (P < 0.05) concentrations of interleukin-4 and interleukin-10 were observed in plasma from pigs fed one of the diets containing torula yeast compared with pigs fed the control diet on d 14. In conclusion, inclusion of either a conventional or a novel source of torula yeast at the expense of animal proteins in diets for weanling pigs may improve intestinal health without influencing growth performance of weanling pigs.

Screening the Lipid Production Potential of Oleaginous Yeast Yarrowia lipolytica under Wood Hydrolysates

Since Yarrowia lipolytica, an oily yeast, contains many valuable products as biomass, to increase its widespread use, it is very important to develop a sustainable production model. In this study, the production of high acid hydrolysate from sawdust biomass, which is produced in very high amounts in our environment, and the effect of these products on the growth efficiency of Yarrowia lipolytica were investigated. A preliminary statistical analysis was carried out to assess sugar production from sawdust by hydrolysis, which estimated 85% of total sugar recovery (TSR) using 96 g of sawdust, while TSR at the highest sawdust was as high as 79%. There was a higher loss in the recovery of C5 sugars with acid and time. This study revealed that Y. lipolytica could grow with high biomass yields in varying hydrolysate concentrations, approaching yields achieved in synthetic glucose media. The maximum biomass obtained was 13 and 26 g in batch and airlift operations, respectively, using organic nutrients. Biomass and lipid yields from kinetic modeling provided a close approximation to the experimental yields performed on an airlift reactor. It was found that Y. lipolytica biomass cultivated on sawdust hydrolysates had significant lipid and protein compositions, as high as 29 and 38%, respectively.

Evaluation of Non-Conventional Yeasts Isolated from Rotten Wood for Hydrolytic Activities and Xylose Fermentation

Hydrolysis of lignocellulose to fermentable sugars and their subsequent conversion to ethanol remain great challenges in the biofuel industry. Rotten wood is first colonized by bacteria and molds that possess strong hydrolases. Yeasts are also an important group of microorganisms that may participate in wood hydrolysis. Decaying wood could provide a rich natural reservoir of yeasts possessing promising hydrolytic activities, including xylanases, cellulases, β-glucosidases, or abilities essential for the fermentation of pentose sugars derived from lignocellulose degradation, especially xylose. Therefore, the aim of this work was to screen yeasts isolated from rotten wood samples for the production of hydrolytic enzymes directed at lignocellulose components and the ability to ferment xylose, L-arabinose, and cellobiose. Methods. Yeast strains were isolated from 22 samples of rotten wood and identified by phenotypic characteristics according to Kurtzman et al. Hydrolytic properties and the ability of the isolated strains to ferment xylose, L-arabinose, and cellobiose were determined using conventional methods. Results. 30 strains of yeasts and yeast-like micromycetes were isolated from 22 samples of rotten wood in the Holosiivskyi Forest, Kyiv. Based on phenotypic properties, most of the isolated yeasts belonged to ascomycetous yeasts and were represented by the following genera: Candida (8 strains), Debaryomyces (5 strains), Kluyveromyces (5 strains), Pichia (5 strains), Scheffersomyces (2 strains), Lachancea, Hanseniaspora, Saccharomyces, and Geotrichum/Galactomyces. A strain of yeast-like non-photosynthetic alga Prototheca sp. was also detected. Most of the isolated microfungi (66.6% isolates) exhibited extracellular β-glucosidase activity, two Candida tropicalis strains possessed weak pectinase and xylanase activity. None of the isolates demonstrated extracellular cellulase activity. Two yeast strains preliminarily identified as Scheffersomyces stipitis were able to ferment xylose at a concentration of 20—100 g/L over a wide temperature range up to 37°C. Acetic acid at 0.25—1% (v/v) concentration resulted in the complete inhibition of xylose fermentation. Ethanol production from xylose up to 6 g/L was observed under the microaerobic fermentation conditions for 24 hr at the substrate concentration 40 g/L, but the subsequent fermentation resulted in decreasing ethanol concentration presumably due to ethanol re-assimilation. None of the isolated strains was capable of fermenting cellobiose or L-arabinose under the microaerobic conditions. Conclusions. This work provides the characterization of yeast microbiota of rotten wood that was represented predominantly by ascomycetous yeasts. The dominant extracellular hydrolytic activity of the isolates was β-glucosidase. This is the first report on the isolation of xylose-fermenting yeasts Scheffersomyces stipitis in Ukraine, which comprised 7% of all the microfungi isolated from rotten wood.

Поведение зольных элементов древесины в процессе кислотного гидролиза древесины

Минеральные вещества помимо большого физиологического значения в развитии растений оказывают значительное влияние на процессы химической и термохимической переработки древесины. В особенности, это важно при проведении кислотных гидролитических процессов углеводного комплекса и связанных с этим процессами нейтрализации кислоты зольными элементами растительных материалов. Исследование поведения зольных элементов древесины в процессе кислотного гидролиза древесины явилось целью настоящей работы. В работе было показано, что зольные вещества древесины березы, легко экстрагируются водой и слабыми растворами кислот при комнатной температуре. При этом водорастворимые вещества составляют– 42,4%, а кислоторастворимые - 63,6% от общего содержания золы в древесине. Анализ способности зольных веществ древесины березы к нейтрализации кислоты показал, что полная нейтрализация составляет - 72,5 мг-экв\кг сухой массы (3,55 г серной кислоты на 1 кг древесины); после водной экстракции – 34,0 мг-экв\кг, а после экстракции растворами кислоты - 9,4-13,6 мг-экв\кг. При проведении гемицеллюлозного гидролиза древесины березы происходит удаление более 85% массы зольных элементов древесины, в том числе более 85% солей кальция, 90% солей магния, 90% фосфора и 63 % калия. Нейтрализующая способность золы при этом составила 62,4мг-экв\кг сухой массы (3,1 г серной кислоты на 1 кг древесины). Выбранный на основании полученных данных режим малокислотного гемицеллюлозного гидролиза древесины при условии 50% нейтрализации серной кислоты зольными элементами (6,25 г\кг сухого сырья). Показал значительно лучшие показатели по скорости гидролиза, содержанию моносахаридов и цветности экстракта по сравнению с автогидролизом. Mineral substances, in addition to their great physiological significance in the development of plants, have a significant effect on the processes of chemical and thermochemical processing of wood. In particular, this is important when carrying out acidic hydrolytic processes of the carbohydrate complex and associated processes of acid neutralization with ash elements of plant materials. The study of the behavior of ash elements of wood in the process of acid hydrolysis of wood was the goal of this work. It was shown in the work that the ash substances of birch wood are easily extracted with water and weak acid solutions at room temperature. At the same time, water-soluble substances make up 42.4%, and acid-soluble ones – 63.6% of the total ash content in wood. Analysis of the ability of ash substances of birch wood to neutralize acid showed that complete neutralization is – 72.5 mg-eq/kg dry weight (3.55 g of sulfuric acid per 1 kg of wood); after water extraction – 34.0 mEq/kg, and after extraction with acid solutions – 9.4-13.6 mEq/kg. When carrying out hemicellulose hydrolysis of birch wood, more than 85% of the mass of ash elements of the wood is removed, including more than 85% of calcium salts, 90% of magnesium salts, 90% of phosphorus and 63% of potassium. At the same time, the neutralizing ability of ash was 62.4 mg-eq/kg of dry weight (3.1 g of sulfuric acid per 1 kg of wood). The mode of low-acid hemicellulose hydrolysis of wood, selected on the basis of the data obtained, under the condition of 50% neutralization of sulfuric acid with ash elements (6.25 g/kg of dry raw materials). Showed significantly better indicators in terms of the rate of hydrolysis, the content of monosaccharides and the color of the extract in comparison with autohydrolysis.

Crabtree Effect on Rhodosporidium toruloides Using Wood Hydrolysate as a Culture Media

The interest in microorganisms to produce microbial lipids at large-scale processes has increased during the last decades. Rhodosporidium toruloides-1588 could be an efficient option for its ability to simultaneously utilize five- and six-carbon sugars. Nevertheless, one of the most important characteristics that any strain needs to be considered or used at an industrial scale is its capacity to grow in substrates with high sugar concentrations. In this study, the effect of high sugar concentrations and the effect of ammonium sulfate were tested on R. toruloides-1588 and its capacity to grow and accumulate lipids using undetoxified wood hydrolysates. Batch fermentations showed a catabolic repression effect on R. toruloides-1588 growth at sugar concentrations of 120 g/L. The maximum lipid accumulation was 8.2 g/L with palmitic, stearic, oleic, linoleic, and lignoceric acids as predominant fatty acids in the produced lipids. Furthermore, R. toruloides-1588 was able to utilize up to 80% of the total xylose content. Additionally, this study is the first to report the effect of using high xylose concentrations on the growth, sugar utilization, and lipid accumulation by R. toruloides-1588.

Carbon/nitrogen ratio as a tool to enhance the lipid production in Rhodosporidium toruloides-1588 using C5 and C6 wood hydrolysates

The interest in microbial lipids has recently increased because of their wide use to produce several value-added compounds in the biofuel, pharmaceutical and food industries. Oleaginous yeast such as Rhodosporidium toruloides could be an efficient option because of its ability to consume five-carbon sugars, high lipid accumulation, and tolerance to toxic compounds such as furans, phenolic compounds, and organic acids. The present study aims to investigate the effect of different initial sugar ratios, in combination with different carbon/nitrogen ratios, and the use of dibasic sodium phosphate (Na2HPO4) as an inducer on cell biomass production, sugar consumption, and lipid accumulation by Rhodosporidium toruloides-1588. The investigation showed a maximum lipid accumulation of 5.35 gL-1 (0.28 g of lipids/g of sugar) under the culture conditions of initial glucose: xylose ratio of 1:1, C/N ratio of 70, and Na2HPO4 concentration of 1.05 gL-1. The predominant lipids composition was palmitic, stearic, oleic, and linoleic acids which could be used as a suitable feedstock for biofuel production. Additionally, under the optimal conditions (initial glucose: xylose ratio of 1:1, 1.19 gL-1 of Na2HPO4 and C/N ratio of 70.50) an increase of 10.5% and 7.5% in lipid accumulation was observed, compared with control treatments (glucose and xylose, respectively). In addition, the study shows the ability of R. toruloides-1588 to tolerate inhibitors, a feature that could be a promising alternative to increase the feasibility of the microbial lipid production process using undetoxified wood hydrolysate as a sustainable culture media.

Evaluating the Effect of Trace Metal Salts on Lipid Accumulation Ability of Rhodosporidium toruloides-1588 Using Wood Hydrolysate as a Carbon Source

Evaluating the Effect of Trace Metal Salts on Lipid Accumulation Ability of Rhodosporidium toruloides-1588 Using Wood Hydrolysate as a Carbon Source

Influence of Pine and Alder Woodchips Storage Method on the Chemical Composition and Sugar Yield in Liquid Biofuel Production.

The aim of this study was to investigate the effect of storing methods of woodchips from two species, pine (Pinus sylvestris L.) and alder (Alnus Mill.), on the basic chemical composition and sugar yield in liquid biofuel production. Two methods of storing woody biomass were used in the study—an open pile and a cover pile. The wood was felled at the end of November and was stored as industrial chips for eight months from December onward. After this time, material was collected for chemical composition analyses and enzymatic hydrolysis. The results of the chemical composition analysis of the wood for both studied species showed the influence of the type of storage on the composition of the individual structural components of the wood. Based on the results of the enzymatic hydrolysis of the woody biomass, it can be seen that, irrespective of the hydrolysed material (wood, cellulose, holocellulose), the material from the biomass stored in the open pile gave higher results. The hydrolysis efficiency also increased with time, independent of the type of material that was hydrolysed. The highest sugar yield from the enzymatic hydrolysis of wood was obtained for alder wood stored in an open pile. The highest sugar yield from the enzymatic hydrolysis of cellulose was obtained for cellulose extracted from alder wood—as well—that had been stored in an open pile.

A co-fermentation strategy with wood hydrolysate and crude glycerol to enhance the lipid accumulation in Rhodosporidium toruloides-1588

Wood hydrolysate has been regarded as sustainable and renewable substrate to produce microbial lipids, a potential feedstock for the biodiesel industry. Moreover, the major by-product of biofuel industries is crude glycerol but its implementation as a carbon source is still constrained due to the presence of impurities resulting in low biomass production and low lipid titer. Thus, this study investigates the effect of different carbon ratios of hydrolysate and crude glycerol on R. toruloides-1588. Hydrolysate to crude glycerol ratio of 60:40 resulted in maximum lipid accumulation of 49% (w/w), more than 90% of sugars and glycerol consumption. Further, scale-up to bench-scale fermenter resulted in 12% higher lipid accumulation (56.3% w/w, 0.15 g/L∙h) in 50% less time than flask fermentation. Hence, the ability of R. toruloides-1588 to flourish on different carbohydrates and accumulate high lipid content will be beneficial for the further development of biorefinery industries.

Furfural degradation and its effect on Rhodosporidium toruloides-1588 during microbial growth and lipid accumulation

The presence of furfural in the hydrolysates obtained from lignocellulosic biomass sources represents an enormous challenge during their fermentation because furfural is a toxic compound for different microorganisms. Rhodosporidium toruloides-1588 can grow and accumulate lipids using wood hydrolysate as a substrate containing up to 1 g/L of furfural. In this study, the capacity of R. toruloides-1588 to grow and accumulate lipids using furfural without glucose in the media has been observed. R. toruloides-1588 degraded up to 3 g/L of furfural into furfuryl alcohol (1.8 g/L) and 2-furoic acid (0.9 g/L). Furthermore, R. toruloides-1588 accumulated 52% and 30% of its dry weight into lipids using YM media and YM media without glucose, respectively. Fatty acids such as palmitic, stearic and oleic were the most abundant. Finally, R. toruloides-1588 could potentially utilize furfural as a carbon source.

Furniture wood waste depollution through hydrolysis under pressurized water steam: Experimental work and kinetic modelization

As the Recycling of wood waste becomes more important each year, wood products that contain urea-formaldehyde resins gained more attention due to the release of formaldehyde and other chemicals which have a critical impact on humans health and the environment. In this study, the hydrolysis of wood wastes from a French furniture industry was studied under different controlled conditions (temperature/pressure, steam ratio). An original on-line method to measure the emission of formaldehyde and ammonia using a FTIR spectrometer and a dilution system was applied successfully in this study. The effect of operatory conditions on formaldehyde and ammonia released is discussed. A mathematical model was also introduced to model the behavior of the ammonia and formaldehyde emission in the hydrolysis of wood waste.

A new approach to zip-lignin: 3,4-dihydroxybenzoate is compatible with lignification.

Summary Renewed interests in the development of bioenergy, biochemicals, and biomaterials have elicited new strategies for engineering the lignin of biomass feedstock plants. This study shows, for the first time, that 3,4‐dihydroxybenzoate (DHB) is compatible with the radical coupling reactions that assemble polymeric lignin in plants.We introduced a bacterial 3‐dehydroshikimate dehydratase into hybrid poplar (Populus alba × grandidentata) to divert carbon flux away from the shikimate pathway, which lies upstream of lignin biosynthesis.Transgenic poplar wood had up to 33% less lignin with p‐hydroxyphenyl units comprising as much as 10% of the lignin. Mild alkaline hydrolysis of transgenic wood released fewer ester‐linked p‐hydroxybenzoate groups than control trees, and revealed the novel incorporation of cell‐wall‐bound DHB, as well as glycosides of 3,4‐dihydroxybenzoic acid (DHBA). Two‐dimensional nuclear magnetic resonance (2D‐NMR) analysis uncovered DHBA‐derived benzodioxane structures suggesting that DHB moieties were integrated into the lignin polymer backbone. In addition, up to 40% more glucose was released from transgenic wood following ionic liquid pretreatment and enzymatic hydrolysis.This work highlights the potential of diverting carbon flux from the shikimate pathway for lignin engineering and describes a new type of ‘zip‐lignin’ derived from the incorporation of DHB into poplar lignin.

Efficient and economical production of polyhydroxyalkanoate from sustainable rubber wood hydrolysate and xylose as co-substrate by mixed microbial cultures

Using co-substrate to accumulate polyhydroxyalkanoate (PHA) is an efficient approach to reduce production cost and improve yield of PHA. In the study, PHA was biosynthesized under full aerobic mode by using rubber wood hydrolysate and xylose co-substrate as the carbon source. The effects of co-substrate on PHA production, microbial community and carbon conversion were explored. The results showed that proper addition of xylose was beneficial for the synthesis of PHA and monomer 3-hydroxyvalerate (3HV). Higher conversion yield of substrate-to-PHA (YPHA/S) of 0.933 g COD PHA/g COD S and PHA content of 43.6 g PHA/100 g VSS were gained at co-substrate ratio of 1:1. Likewise, under this condition, PHA production also reached the highest value of 1849 mg COD/L (1088 mg/L). Moreover, the addition of xylose created a favorable screening of PHA dominant strains, improved the conversion of carbon source, and saved 72.3% of feedstock consumption.

Inhibitor degradation by Rhodosporidium toruloides NRRL 1588 using undetoxified wood hydrolysate as a culture media

Lignocellulosic biomass has been identified as a renewable and sustainable feedstock to produce liquid hydrolysates as a suitable substrate to produce a variety of compounds through biochemical processes. Nevertheless, the main challenge to using this substrate is the hydrolysis needed to release fermentable sugars. This pretreatment leads to the production of microbial toxic compounds such as furans, phenols and organic acids. In this work, an oleaginous yeast, R. toruloides NRRL 1588, was used to study its ability to degrade inhibitors in C5 and C6 wood hydrolysates obtained from forestry residues. The study showed that R. toruloides NRRL 1588 can grow, accumulate lipids, and degrade up to 8.01 mgL−1 h−1 of furfural, 5.63 mgL−1 h−1 of 5-hydroxy methyl furfural, 1.70 mgL−1 h−1 of levulinic acid, 1.15 mgL−1 h−1 of syringaldehyde, 0.67 mgL−1 h−1 of vanillin, and 1.03 mgL−1 h−1 of vanillic acid. This work confirms the robustness of R. toruloides NRRL 1588 when grows in wood hydrolysates containing inhibitory compounds.