Biorefineries--multi product processes

Pharmaceutical Assessment of Watermelon Rind Pectin as a Suspending Agent in Oral Liquid Dosage Forms

Pectin is a high molecular weight polymer which is present in virtually all plants where it contributes to the cell structure. Pectin is a high valuable food ingredient widely used as a gelling agent and thickening agent with limited use in the pharmaceutical industry. The objective of this study is to evaluate the suspending properties of pectin from watermelon rind. Tragacanth was used as a standard suspending agent to which the suspending properties of pectin from watermelon rinds were compared with. The extracted pectin was subjected to phytochemical and physiochemical characterization for its safety and suitability to use as a suspending agent. Paracetamol suspensions were formulated using tragacanth concentrations of 0.5% w/v, 1% w/v, and 2% w/v and compared with paracetamol suspensions containing the same concentrations of watermelon pectin. The suspensions were all tested for their pH, sedimentation rate, sedimentation volume, flow rate, and ease of redispersibility over a period of 4 weeks. At the end of the 4-week period, all formulated suspensions had no changes in their pH values. Suspensions containing the extracted pectin had a lower rate of sedimentation and ease of redispersibility compared to that of tragacanth. In addition, their sedimentation volumes as well as flow rates were comparable to that of the tragacanth formulations. Ultimately, pectin from watermelon rind can serve as a suitable alternative to tragacanth in formulation of pharmaceutical suspensions.

The role of biorefinering research in the development of a modern bioeconomy

The current economy system is based in an intensive consumption of fossil fuels in a way that severely compromise future of the planet due to the severe consequences in climate change. In this scenario, the development of flexible and integrated biorefineries to produce biofuels and bioproducts from renewable biomass sources represent a key tool to perform the transition from a petroleum-based economy to a novel bioeconomy that looks for a more efficient and sustainable global development. This article analyses: the significance of biomass sources (such as agricultural and woody crops and residues, agro-food and wood processing industries residues and urban wastes) as feedstocks in the biorefinery, the most relevant biorefinering process technologies of the biochemical and thermochemical conversion pathways that are nowadays under development, and the need of further research and innovation effort to eventually achieve the commercialization and application in the market of the different biorefinery products.

Chromatographic Recovery of Monosaccharides and Lignin from Lignocellulosic Hydrolysates

The chromatographic recovery of monosaccharides and lignin from lignocellulosic hydrolysates was studied at laboratory and pilot scale. A weak cation-exchange resin in sodium form and a water eluent gave good separation efficiency. Scale-dependent phenomena, especially viscous fingering resulting from the large viscosity and density differences between the hydrolysate feed and eluent, were observed. The issue was resolved in the pilot scale with appropriate selection of the flow direction, and a high productivity was achieved at 95 % recovery yield. The pH value of the feed was found to have no effect on the actual separation; however, the resin was significantly less colored at a higher pH value.

Enhancement of cell growth and phycocyanin production in Arthrospira (Spirulina) platensis by metabolic stress and nitrate fed-batch

Arthrospira (Spirulina) platensis is known to have high-quality proteins content and phycocyanin as one of the major pigment constituents of the cells, and the most challenging problem associated with phycocyanin production in Arthrospira is to optimize its intracellular accumulation. The present study evaluated the metabolic stress conditions (by nutrient enrichment) of Arthrospira platensis FACHB-314 for boosting biomass growth and high content phycocyanin accumulation. Experimental results showed that 5 mM sodium glutamate and 7.5 mM succinic acid could enhance biomass yield as well as phycocyanin accumulation compared with that of the control groups. The present study demonstrates that the biomass growth and phycocyanin accumulation were significantly enhanced in fed-batch cultivation of Arthrospira platensis by applying the substrates as metabolic stress agents combined with nitrate feeding strategy. cobA/hemD, hemG and ho genes presented the over-expression level with adding sodium glutamate and succinic acid in cultures, respectively, compared to the control groups.

Synergistic action between extracellular products from white-rot fungus and cellulase significantly improves enzymatic hydrolysis

With a set of perfect extracellular lignocellulolytic enzymes, white-rot fungus has been recognized as playing an important role in the degradation of lignocellulose materials, which leads to the possibility of creating a composite enzymatic system with high hydrolysis efficiency in vitro. Echinodontium taxodii is a promising white-rot fungus for biologic pretreatment. In this study, we extracted the extracellular products of E. taxodii under solid-state fermentation conditions, mixed the extracellular products with cellulase to build a composite enzymatic system, and systematically evaluated the effect of this system on the hydrolysis of acid-pretreated and raw maize stovers. We found that the extracellular products from E. taxodii could significantly improve the hydrolysis efficiency of cellulase, with a synergistic action between the extracellular products and cellulase. Corn stovers treated with extracellular products were suitable for the enzymatic hydrolysis of cellulase. Furthermore, we found that pure proteins from the extracellular products were not sufficient to generate synergistic action. This finding suggests that non-protein substances may also be involved in the synergistic action between the extracellular products and cellulase.

Simultaneous production of intracellular triacylglycerols and extracellular polyol esters of fatty acids by Rhodotorula babjevae and Rhodotorula aff. paludigena

Microbial oils have been analyzed as alternatives to petroleum. However, just a handful of microbes have been successfully adapted to produce chemicals that can compete with their petroleum counterparts. One of the reasons behind the low success rate is the overall economic inefficiency of valorizing a single product. This study presents a lab-scale analysis of two yeast species that simultaneously produce multiple high-value bioproducts: intracellular triacylglycerols (TG) and extracellular polyol esters of fatty acids (PEFA), two lipid classes with immediate applications in the biofuels and surfactant industries. At harvest, the yeast strain Rhodotorula aff. paludigena UCDFST 81-84 secreted 20.9 ± 0.2 g L^-1 PEFA and produced 8.8 ± 1.0 g L^-1 TG, while the yeast strain Rhodotorula babjevae UCDFST 04-877 secreted 11.2 ± 1.6 g L^-1 PEFA and 18.5 ± 1.7 g L^-1 TG. The overall glucose conversion was 0.24 and 0.22 g_{(total lipid)} g _(glucose)^-1 , respectively. The results present a stable and scalable microbial growth platform yielding multiple co-products.

Visualising recalcitrance by colocalisation of cellulase, lignin and cellulose in pretreated pine biomass using fluorescence microscopy

Mapping the location of bound cellulase enzymes provides information on the micro-scale distribution of amenable and recalcitrant sites in pretreated woody biomass for biofuel applications. The interaction of a fluorescently labelled cellulase enzyme cocktail with steam-exploded pine (SEW) was quantified using confocal microscopy. The spatial distribution of Dylight labelled cellulase was quantified relative to lignin (autofluorescence) and cellulose (Congo red staining) by measuring their colocalisation using Pearson correlations. Correlations were greater in cellulose-rich secondary cell walls compared to lignin-rich middle lamella but with significant variations among individual biomass particles. The distribution of cellulose in the pretreated biomass accounted for 30% of the variation in the distribution of enzyme after correcting for the correlation between lignin and cellulose. For the first time, colocalisation analysis was able to quantify the spatial distribution of amenable and recalcitrant sites in relation to the histochemistry of cellulose and lignin. This study will contribute to understanding the role of pretreatment in enzymatic hydrolysis of recalcitrant softwood biomass.

Structural and functional studies of the glycoside hydrolase family 3 β-glucosidase Cel3A from the moderately thermophilic fungus Rasamsonia emersonii

The filamentous fungus Hypocrea jecorina produces a number of cellulases and hemicellulases that act in a concerted fashion on biomass and degrade it into monomeric or oligomeric sugars. β-Glucosidases are involved in the last step of the degradation of cellulosic biomass and hydrolyse the β-glycosidic linkage between two adjacent molecules in dimers and oligomers of glucose. In this study, it is shown that substituting the β-glucosidase from H. jecorina (HjCel3A) with the β-glucosidase Cel3A from the thermophilic fungus Rasamsonia emersonii (ReCel3A) in enzyme mixtures results in increased efficiency in the saccharification of lignocellulosic materials. Biochemical characterization of ReCel3A, heterologously produced in H. jecorina, reveals a preference for disaccharide substrates over longer gluco-oligosaccharides. Crystallographic studies of ReCel3A revealed a highly N-glycosylated three-domain dimeric protein, as has been observed previously for glycoside hydrolase family 3 β-glucosidases. The increased thermal stability and saccharification yield and the superior biochemical characteristics of ReCel3A compared with HjCel3A and mixtures containing HjCel3A make ReCel3A an excellent candidate for addition to enzyme mixtures designed to operate at higher temperatures.

Acidic ionic liquids as sustainable approach of cellulose and lignocellulosic biomass conversion without additional catalysts

The use of ionic liquids (ILs) for biomass processing has attracted considerable attention recently as it provides distinct features for pre-treated biomass and fractionated materials in comparison to conventional processes. Process intensification through integration of dissolution, fractionation, hydrolysis and/or conversion in one pot should be accomplished to maximise economic and technological feasibility. The possibility of using alternative ILs capable not only of dissolving and deconstructing selectively biomass but also of catalysing reactions simultaneously are a potential solution of this problem. In this Review a critical overview of the state of the art and perspectives of the hydrolysis and conversion of cellulose and lignocellulosic biomass using acidic ILs using no additional catalyst are provided. The efficiency of the process is mainly considered with regard to the hydrolysis and conversion yields obtained and the selectivity of each reaction. The process conditions can be easily tuned to obtain sugars and/or platform chemicals, such as furans and organic acids. On the other hand, product recovery from the IL and its purity are the main challenges for the acceptance of this technology as a feasible alternative to conventional processes.

Identification of a genomic region containing a novel promoter resistant to glucose repression and over-expression of β-glucosidase gene in Hypocrea orientalis EU7-22

A high concentration of glucose in the medium could greatly inhibit the expression of cellulase in filamentous fungi. The aspartic protease from fungus Hypocrea orientalis EU7-22 could efficiently express under both induction condition and glucose repression condition. Based on the sequence of structure gene of aspartic protease, the upstream sequence harboring the putative promoter proA for driving the expression of aspartic protease was obtained by genome walking. The upstream sequence contained the typical promoter motifs “TATA” and “CAAT”. The β-glucosidase gene (Bgl1) from H. orientalis was cloned and recombined with promoter proA and terminator trpC. The expression cassette was ligated to the binary vector to form pUR5750-Bgl1, and then transferred into the host strain EU7-22 via Agrobacterium tumefaciens mediated transformation (ATMT), using hygromycin B resistance gene as the screening marker. Four transformants Bgl-1, Bgl-2, Bgl-3 and Bgl-4 were screened. Compared with the host strain EU7-22, the enzyme activities of filter paper (FPA) and β-glucosidase (BG) of transformant Bgl-2 increased by 10.6% and 19.1% under induction condition, respectively. The FPA and BG activities were enhanced by 22.2% and 700% under 2% glucose repression condition, respectively, compared with the host strain. The results showed that the putative promoter proA has successfully driven the over-expression of Bgl1 gene in H. orientalis under glucose repression condition.

The promoting effect of byproducts from Irpex lacteus on subsequent enzymatic hydrolysis of bio-pretreated cornstalks

BACKGROUND

Irpex lacteus, a versatile lignin-degrading fungus with various extracellular enzymes, has been widely used for biological pretreatment. However, most studies have focused on the change of substrate structure after biological pretreatment, and the effect of these changes on the enzymatic hydrolysis, but the effect of byproducts from biological pretreatment process on subsequent enzymatic hydrolysis is not well understood.

METHODS

We developed a biological pretreatment process with I. lacteus that can produce stimulatory byproducts that enhance the enzymatic hydrolysis of cornstalks.

RESULTS

The maximum hydrolysis yield of glucan (82%) was obtained after pretreatment for 28 days. The maximum reducing sugar yield decreased from 313.5 to 200.1 mg/g raw cornstalks after water-soluble byproducts of biological pretreatment were removed from pretreated cornstalks. The effect of byproducts on enzymatic hydrolysis was also investigated. We found that the hydrolysis efficiency of commercial cellulase preparation on cornstalks could be improved by water extracts from bio-pretreated cornstalks with hydrolytic enzyme activity and iron-reducing activity.

CONCLUSION

The key finding suggested that byproducts from biological pretreatment play important roles in enhancing downstream hydrolysis, which might be attributable to hydrolytic enzymes and iron-reducing compounds produced by I. lacteus.

A biorefinery processing perspective: treatment of lignocellulosic materials for the production of value-added products

In the last decade, there has been increasing research interest in the value of bio-sourced materials recovered from residual biomass. Research that focuses on the use of extracted, recovered and/or synthesized bioproducts for direct industrial applications is essential for the implementation of sustainable approaches in a forward-looking bio-based economy. The effective use of biomass feedstocks, particularly lignocellulosic materials (plant biomass predominantly comprised of cellulose, hemicellulose, and lignin), in large-scale applications will evolve from innovative research aimed at the development and implementation of biorefineries--multi-step, multi-product facilities established for specific bio-sourced feedstocks. This paper presents recent advances in lignocellulosic biomass processing and analysis from a biorefining perspective. In addition, existing industrial biomass processing applications are discussed and examined within a biorefinery context.

An evolved xylose transporter from Zymomonas mobilis enhances sugar transport in Escherichia coli

Background

Xylose is a second most abundant sugar component of lignocellulose besides glucose. Efficient fermentation of xylose is important for the economics of biomass-based biorefineries. However, sugar mixtures are sequentially consumed in xylose co-fermentation with glucose due to carbon catabolite repression (CCR) in microorganisms. As xylose transmembrance transport is one of the steps repressed by CCR, it is therefore of interest to develop a transporter that is less sensitive to the glucose inhibition or CCR.

Results

The glucose facilitator protein Glf transporter from Zymomonas mobilis, also an efficient transporter for xylose, was chosen as the target transporter for engineering to eliminate glucose inhibition on xylose uptake. The evolution of Glf transporter was carried out with a mixture of glucose and xylose in E. coli. Error-prone PCR and random deletion were employed respectively in two rounds of evolution. Aided by a high-throughput screening assay using xylose analog p-nitrophenyl-β-D-xylopyranoside (pNPX) in 96-well plates, a best mutant 2-RD5 was obtained that contains several mutations, and a deletion of 134 residues (about 28% of total residues), or three fewer transmembrane sections (TMSs). It showed a 10.8-fold improvement in terms of pNPX transport activity in the presence of glucose. The fermentation performance results showed that this mutant improved xylose consumption by 42% with M9 minimal medium containing 20 g L^-1 xylose only, while with the mixture sugar of xylose and glucose, 28% more glucose was consumed, but no obvious co-utilization of xylose was observed. Further glucose fed-batch experiments suggested that the intracellular metabolism of xylose was repressed by glucose.

Conclusions

Through random mutagenesis and partial deletion coupled with high-throughput screening, a mutant of the Glf transporter (2-RD5) was obtained that relieved the inhibition of xylose transport by glucose. The fermentation tests revealed that 2-RD5 was advantageous in xylose and glucose uptakes, while no obvious advantage was seen for xylose co-consumption when co-fermented with glucose. Further efforts could focus on reducing CCR-mediated repression of intracellular metabolism of xylose. Glf should also serve as a useful model to further exploit the molecular mechanism of xylose transport and the CCR-mediated inhibition.

Gold-catalyzed aerobic oxidation of 5-hydroxymethylfurfural in water at ambient temperature

The aerobic oxidation of 5-hydroxymethylfurfural, a versatile biomass-derived chemical, is examined in water with a titania-supported gold-nanoparticle catalyst at ambient temperature (30 °C). The selectivity of the reaction towards 2,5-furandicarboxylic acid and the intermediate oxidation product 5-hydroxymethyl-2-furancarboxylic acid is found to depend on the amount of added base and the oxygen pressure, suggesting that the reaction proceeds via initial oxidation of the aldehyde moiety followed by oxidation of the hydroxymethyl group of 5-hydroxymethylfurfural. Under optimized reaction conditions, a 71% yield of 2,5-furandicarboxylic acid is obtained at full 5-hydroxymethylfurfural conversion in the presence of excess base.