Optimization of Pre-treatment Using RSM on Wheat Straw and Production of Lactic Acid Using Thermotolerant, Inhibitor Tolerant and Xylose Utilizing Bacillus Sonorenesis Strain DGS15

Thermotolerant lactic acid producing bacteria, isolated from red soil of brick kiln was identified by 16S rRNA sequencing as Bacillus sonorenesis , which showed remarkable capability to ferment sugars of lignocellulosic biomass after pre-treatment, yielding 0.97 g/g lactic acid with overall productivity of 0.38 g L -1/ h. RSM was employed to optimize the sulphuric acid pre-treatment combined with dilute NaOH and hot water pre-treatment. Pretreated wheat straw biomass had 40.4% cellulose, 18.4% hemicellulose, 12.4% lignin and 28.2 g L -1 reducing sugar, while native wheat straw biomass had 36% cellulose, 25% hemicellulose, 20% total lignin, and 0.94 g L -1 reducing sugar. Scanning electron microscopy (SEM) revealed that the ordered and compact structure of wheat straw was destroyed upon pre-treatment. X-ray diffractogram (XRD) revealed 9.71% increase in crystallinity index ( CrI ) in pretreated biomass. FTIR spectrogram showed removal of lignin due to reduction of peak at 1640 cm -1 in pretreated biomass. Bacillus sonorenesis DGS15 is inhibitor tolerant (furfural (1.2 g L -1 ) and HMF (2.4 g L -1 )). Furfural was consumed after 72 h of fermentation and HMF got accumulated with 3.75-fold increase in concentration in the fermentation broth. In terms of final concentration, yield, and fermentation duration, this is the best performance of DGS15 for lactic acid production utilizing xylose, glucose as the carbon source. All of these findings showed that the thermotolerant Bacillus sonorenesis strain DGS15 is a novel, attractive candidate for producing lactic acid from lignocellulosic biomass.

Production of Omega-3 Fatty Acids from the Microalga Crypthecodinium cohnii by Utilizing Both Pentose and Hexose Sugars from Agricultural Residues

The core objective of this work was to take advantage of the unexploited wheat straw biomass, currently considered as a broadly available waste stream from the Greek agricultural sector, towards the integrated valorization of sugar streams for the microbial production of polyunsaturated omega-3 fatty acids (PUFAs). The OxiOrganosolv pretreatment process was applied using acetone and ethanol as organic solvents without any additional catalyst. The results proved that both cellulose-rich solid pulp and hemicellulosic oligosaccharides-rich aqueous liquid fraction after pretreatment can be efficiently hydrolyzed enzymatically, thus resulting in high yields of fermentable monosaccharides. The latter were supplied as carbon sources to the heterotrophic microalga Crypthecodinium cohnii for the production of PUFAs, more specifically docosahexaenoic acid (DHA). The solid fractions consisted mainly of hexose sugars and led to higher DHA productivity than their pentose-rich liquid counterparts, which can be attributed to the different carbon source and C/N ratio in the two streams. The best performance was obtained with the solid pulp pretreated with ethanol at 160 °C for 120 min and an O2 pressure of 16 bar. The total fatty acids content reached 70.3 wt% of dried cell biomass, of which 32.2% was DHA. The total DHA produced was 7.1 mg per g of untreated wheat straw biomass.

Bio-Degradable Polyurethane Foams Produced by Liquefied Polyol from Wheat Straw Biomass

In the present work, an abundant and unused residue (wheat straw) has been employed to synthesize a polyol as a substituent of castor oil in polyurethane foams. The liquefied product showed excellent properties for the proposed application. Castor oil was substituted with up to 50% wheat straw polyol in the formulation of polyurethane foams, which were prepared using two different isocyanates (methylene diphenyl diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI)). The evaluation of physical, mechanical, and thermal properties of the foams revealed that these materials can successfully be formed with up to 40% wheat straw polyols since all the results were improved. Moreover, at this polyol concentration, the morphology of the foams was presented as a compact and ordered structure. Following this trend, the foams showed excellent biodegradability at 30 days (5.60 and 7.31% for TDI and MDI foams, respectively) and 60 days (8.49 and 9.88% for TDI and MDI foams, respectively) in the soil media tests carried out. Thus, the materials prepared in this work can be proposed for agricultural applications such as use in plant nurseries.

Physical and calorific properties of wheat straw briquettes and pellets

Wheat straw briquettes are high performance combustible products obtained by densification from the wheat straw biomass without the use of additional adhesives or additives. The purpose of the paper is to analyze and to detail the physical properties (SR EN ISO / CEI 322 for moisture content by method of drying and weighing, and effective density method according to SR EN ISO / CEI 323: 2005) and calorific properties of these briquettes (high and low calorific value according to ÖNORM M7135 using the XRY-1C / China Calorimeter and ash content according to ASTM D1102-84: 2013 and ISO 18122: 2015) and to make a comparison between these briquettes and other briquettes obtained from wooden biomass. The tested briquettes had a moisture content of 8%, an effective density of 1214 kg/m3, a high calorific value of 17.670 MJ/kg, the low of 17.525 MJ/kg and an ash content of 5.6%. All these values correspond to the permissible limits of the standards in the field. The final conclusion of the paper shows that wheat straw briquettes had physical and calorific properties similar to those of wooden biomass.

New pentose dimers with bicyclic moieties from pretreated biomass

Dipentoses with bicyclic moieties are proposed as new putative cellulase inhibitory reaction products forming during hydrothermal wheat straw biomass pretreatment.