Evaluation of the Simultaneous Production of Xylitol and Ethanol from Sisal Fiber

An Integrated Process for the Xylitol and Ethanol Production from Oil Palm Empty Fruit Bunch (OPEFB) Using Debaryomyces hansenii and Saccharomyces cerevisiae

Oil palm empty fruit bunch (OPEFB) is the largest biomass waste from the palm oil industry. The OPEFB has a lignocellulose content of 34.77% cellulose, 22.55% hemicellulose, and 10.58% lignin. Therefore, this material’s hemicellulose and cellulose content have a high potential for xylitol and ethanol production, respectively. This study investigated the integrated microaerobic xylitol production by Debaryomyces hansenii and anaerobic ethanol semi simultaneous saccharification and fermentation (semi-SSF) by Saccharomyces cerevisiae using the same OPEFB material. A maximum xylitol concentration of 2.86 g/L was obtained with a yield of 0.297 g/g_xylose. After 96 h of anaerobic fermentation, the maximum ethanol concentration was 6.48 g/L, corresponding to 71.38% of the theoretical ethanol yield. Significant morphological changes occurred in the OPEFB after hydrolysis and xylitol and ethanol fermentation were shown from SEM analysis.

An overview of the metabolically engineered strains and innovative processes used for the value addition of biomass derived xylose to xylitol and xylonic acid

Xylose, the most abundant pentose sugar of the hemicellulosic fraction of lignocellulosic biomass, has to be utilized rationally for the commercial viability of biorefineries. An effective pre-treatment strategy for the release of xylose from the biomass and an appropriate microbe of the status of an Industrial strain for the utilization of this pentose sugar are key challenges which need special attention for the economic success of the biomass value addition to chemicals. Xylitol and xylonic acid, the alcohol and acid derivatives of xylose are highly demanded commodity chemicals globally with plenty of applications in the food and pharma industries. This review emphasis on the natural and metabolically engineered strains utilizing xylose and the progressive and innovative fermentation strategies for the production and subsequent recovery of the above said chemicals from pre-treated biomass medium.

Intrinsically radiopaque and antimicrobial cellulose based surgical sutures from mechanically powerful Agave sisalana plant leaf fibers

The judicious configuration of a flexible radiopaque suture would be exemplary to facilitate effortless tracking and precise diagnosis of the sutured surgical site by various X-ray assisted imaging modalities and simultaneously serve as a complementary tool for monitoring the fate of the suture material during the post-operative course. A unique radiopaque cellulose based surgical suture (RF) with good mechanical properties was developed by strategically controlled mercerization and bleaching of mechanically strong natural cellulosic fibers extracted from Agave sisalana plant leaves followed by the facile dip-coating of SrO integrated polylactic acid (PLA). RF exhibited admirable straight-pull tensile strength (184 MPa) and commendable contrast enhancement (277.4%) under digital X-ray radiographic imaging which was further validated by micro-CT analysis. Further, RF has a controlled hydrolytic degradation profile favorable for surgical suturing (mass loss ∼22% in 28 days). The microporous surface architecture of RF (pore size < 10 μm) as a result of SrO-PLA coating enabled the loading of antibiotic (ciprofloxacin) deep inside the pores with a cumulative release of 24% at 28 days under physiological conditions substantiating its feasibility to be used as an efficient antimicrobial suture (CRF) that prevents possible bacterial infections at the surgical site. This has been demonstrated by antibacterial disc diffusion assay performed against two Gram-positive and two Gram-negative bacterial strains. Significantly, both RF and CRF are highly biocompatible as confirmed by MTT assay and F-actin staining. Hence, CRF would be a good biocompatible suture candidate holding good tensile properties, exceptional antimicrobial property and intrinsic radiopacity retention for a period >28 days.

Effect of thermo-chemical pretreatment on the saccharification and enzymatic digestibility of olive mill stones and their bioconversion towards alcohols

The present study investigated the effect of thermo-chemical pretreatment on the enhancement of enzymatic digestibility of olive mill stones (OMS), as well as its possible valorisation via bioconversion of the generated free sugars to alcohols. Specifically, the influence of parameters such as reaction time, temperature, type and concentration of dilute acids and/or bases, was assessed during the thermo-chemical pretreatment. The hydrolysates and the solids remaining after pretreatment, as well as the whole pretreated slurries, were further evaluated as potential substrates for the simultaneous production of ethanol and xylitol via fermentation with the yeast Pachysolen tannophilus. The digestibility and overall saccharification of OMS were considerably enhanced in all cases, with the maximum enzymatic digestibility observed for dilute sodium hydroxide (almost 4-fold) which also yielded the highest total saccharification yield (91% of the total OMS carbohydrates). Ethanol and xylitol yields from the untreated OMS were 28 g/kg OMS and 25 g/kg OMS, respectively, and were both significantly enhanced by pretreatment. The highest ethanol yield was 79 g/kg OMS and was achieved by the alkali pretreatment and separate fermentation of hydrolysates and solids, whereas the highest xylitol yield was 49 g/kg OMS and was obtained by pretreatment with sulphuric acid and separate fermentation of hydrolysates and solids.

Pretreatment of Mango (Mangifera indica L. Anacardiaceae) Seed Husk for Bioethanol Production by Dilute Acid Treatment and Enzymatic Hydrolysis

One of the targets of the Sustainable Development Goals is clean and affordable energy. This is also the aim of the Biofuels Act of 2007 in the Philippines. However, this law is confronted with challenges such as the limitation of lignocellulosic feedstock, specifically available for bioethanol production. The present study sought to address the issue by exploring the potential of mango seed husk (MSH), a by-product of the mango industry, in bioethanol production. MSH is considered a waste material and its utilization also permit value-addition as this can serve as an alternative and affordable source of feedstock in energy production. Two pretreatment strategies are employed to exploit the cellulose and hemicellulose content of MSH, namely, dilute acid treatment and enzymatic hydrolysis. Results show that the %H₂SO₄ resulting in the highest glucose concentration and yield is 4% v/v at 95 °C hydrolysis temperature, 1:10 (w/v) solid-to-solvent ratio, and 60-min hydrolysis time. For enzymatic hydrolysis using a commercial enzyme preparation, the reaction time up to 72 h did not affect glucose concentration and yield at the following conditions: 50 °C hydrolysis temperature, 150 rpm, pH 5.0, 10% solids loading, and 4% enzyme loading. This could be attributed to the lignin and non-structural compounds present in MSHs. However, a combined process strategy of dilute acid pretreatment followed by enzymatic hydrolysis in the pretreatment of MSH contributes to an increased concentration and yield of sugars in the hydrolysates, which is advantageous for bioethanol production. Graphical Abstract.

Preparation and Coagulation Performance of Carboxypropylated and Carboxypentylated Lignosulfonates for Dye Removal

In this work, 1-carboxypropyled (1-CPRLS) and 5-carboxypentyled lignosulfonates (5-CPELS) were synthesized using 2-chlorobutanoic acid and 6-chlorohexanoic acid as carboxylate group donors via S_N1 and S_N2 mechanisms, respectively. 1-Carboxypropyl and 5-carboxypentyl lignosulfonates with the charge densities of −3.45 and −2.94 meq g⁻¹ and molecular weights of 87,900 and 42,400 g·mol⁻¹ were produced, respectively, under mild conditions. The carboxylate content and degree of substitution (DS) of the 1-CPRLS product were 2.37 mmol·g⁻¹ and 0.70 mol·mol⁻¹, while those of 5-CPELS products were 2.13 mmol·g⁻¹ and 0.66 mol·mol⁻¹, respectively. The grafting of carboxypropyl and carboxypentyl groups to lignosulfonate was confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (¹H-NMR and ¹³C-NMR) spectroscopies. In addition, 1-CPRLS and 5-CPELS were applied as coagulants for removing ethyl violet (EV) dye from a simulated solution, and their performance was related to their charge densities and molecular weights. Furthermore, fundamental discussion is provided on the advantages of (1) producing 1-CPRLS and (2) the superior properties and performance of 1-CPRLS to carboxyethylated lignosulfonate.

Molecular modelling studies on adamantane-based Ebola virus GP-1 inhibitors using docking, pharmacophore and 3D-QSAR

The pathogenic Ebola virus (EBOV) causes a potential health risk and global spread. To date, few drugs are available for the treatment of Ebola virus disease (EVD) that allow researchers to use computational methods for designing potential drugs. The developed PHASE-based common six-point pharmacophore hypothesis (AADHPR_1) showed the necessity of two hydrogen bond acceptor features, one hydrogen bond donor feature, one hydrophobic group feature, one positively ionizable and one aromatic ring feature for further designing. We developed best 3D-QSAR models with high regression coefficients for the training (r²>0.82) and test (Q²>0.5) sets for both atoms-based and field-based 3D-QSAR models. The molecule 1A-4 (docking score = -4.711 kcal/mol) was obtained as best docked (SP mode) on Ebola virus envelope glycoprotein (PDB ID-3CSY) as compared with the standards oseltamivir (docking score = -4.39 kcal/mol) and zanamivir (docking score = -3.392 kcal/mol). The obtained ZINC hit ZINC58935541 showed a good docking score of -4.892 kcal/mol. The ZINC58935541 molecule also showed a strong binding affinity towards the receptor cavity of Ebola virus envelope glycoprotein when simulated for 1.2 ns. The good QikProp parameters reflect the fact that this molecule, upon optimization into a lead, might become a good candidate for the treatment of EVD.