Production of fermentable sugars by combined chemo-enzymatic hydrolysis of cellulosic material for bioethanol production

Consolidated bioprocesses for efficient bioconversion of palm biomass wastes into biodiesel feedstocks by oleaginous fungi and yeasts

Consolidated bioprocesses for bioconversion of lignocellulosic biomass into biodiesel feedstocks were developed. Palm empty fruit bunch (EFB) was biologically pretreated coupling with fungal lipid production (121.4 ± 2.7 mg/g-EFB) by lignocellulolytic oleaginous fungi prior to lipid production by oleaginous yeasts. In subsequent separate hydrolysis and fermentation (SHF) of fungal pretreated EFB (FPEFB), the oleaginous yeast with the maximum lipid yield of 37.0 ± 0.1 mg/g-FPEFB was screened. While a higher lipid yield of 47.9 ± 1.5 mg/g-FPEFB was achieved in simultaneous saccharification and fermentation (SSF) with less enzyme requirement. Fed-batch SSF of non-sterile FPEFB was proven as a practical and efficient strategy to increase lipid yield up to 53.4 ± 0.5 mg/g-FPEFB. Total lipid yield by both fungi and yeast was 165.0 ± 4.4 mg/g-EFB. Interestingly, the consolidated bioprocesses of enzyme and lipid production also achieved comparable total lipid yield of 149.3 ± 6.6 mg/g-EFB. These strategies may contribute greatly to cost-effective and sustainable bioconversion of lignocellulosic biomass into biodiesel feedstocks.

Pitfalls in the 3, 5-dinitrosalicylic acid (DNS) assay for the reducing sugars: Interference of furfural and 5-hydroxymethylfurfural

Transformation of renewable biomass into value-added chemicals and biofuels has evolved to be a vital field of research in recent years. Accurate estimation of reducing sugars post pretreatment of lignocellulosic biomass has been very inconsistent. For a few decades, 3,5-dinitrosalicylic acid (DNS) assay has been widely employed for the estimation of reducing sugars derived from pretreatment of lignocellulosic biomass. This assay tests for the presence of free carbonyl group (C=O), the so-called reducing sugars. This involves the oxidation of the aldehyde functional group present to the corresponding acid while DNS is simultaneously reduced to 3-amino-5-nitrosalicylic acid under alkaline conditions. However, the presence of other active carbonyl groups can potentially also react with DNS leading to incorrect yields of reducing sugars. Therefore, a detailed study has been carried out to evaluate the influence of active carbonyl compounds like furfural and 5-hydroxymethylfurfural (5-HMF) in the overall estimation of reducing sugars (glucose, xylose and arabinose) by DNS assay. In addition to this, reducing sugars estimation in the presence of furans were also investigated, it reveals that reducing sugars estimation was found to be 68% higher than actual sugars. Therefore, current findings strongly indicate that the employment of DNS assay for quantifying the reducing sugars in the presence of furans is not appropriate.

Effect of pretreatment with organic solvent on enzymatic digestibility of cauliflower wastes

The present study investigated the operational conditions for different pretreatment approaches and subsequent enzymatic hydrolysis of cauliflower wastes (stalk and leaf) for better release of fermentable sugars. The structural analysis of raw and pretreated lignocellulosic biomasses was investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transforms infrared (FTIR) analysis. Results demonstrated that the highest cellulose conversion rate and removal of most of the hemicellulose and lignin were obtained with organosolvent pretreatment. Using methanol in presence of sodium (Na) acetate was most effective in delignification of cauliflower wastes. In the present study, methanol (100% v/v) in presence of 0.1 M Na-acetate at 121 °C for 45 and 60 min for stalk and leaf, respectively, gave maximum reducing sugar yield. Response surface methodology was used to optimize different process parameters for enzymatic saccharification using microbial cellulase and xylanase. The optimum operation condition of enzymatic hydrolysis of organosolvent pretreated cauliflower wastes were substrate loading (2.5% w/v for both stalk and leaf), enzyme loading (15 and 10 U/g for stalk and leaf, respectively), pH (4.46 and 5.48 for stalk and leaf, respectively), at 60 °C and for 180 min.

Functionalized biochar derived from heavy metal rich feedstock: Phosphate recovery and reusing the exhausted biochar as an enriched soil amendment

This paper provides a circular win-win approach for recycling rhizofiltration biomass into multifunctional engineered biochar for various environmental applications (e.g. phosphate recovery) with a potential reuse of the exhausted biochar as an enriched soil amendment. Functionalized biochars were derived from the disposals of water hyacinth (Eichhornia crassipes) plants grown in synthetic contaminated water spiked with either Fe²⁺ (Fe-B), Mn²⁺ (Mn-B), Zn²⁺ (Zn-B) or Cu²⁺ (Cu-B) comparing with the original drainage water as a control treatment (O-B). The in-situ functionalization of biochar via the inherently heavy metal-rich feedstock produced homogenous organo-mineral complexes on biochar matrix without environmental hazards (e.g. volatilization or chemical sludge formation) associated with other post-synthetic functionalization methods. Physicochemical analyses (SEM-EDS, XRD, FTIR, BET and zeta potential (ζ)) confirmed the functionalization of Fe-B, Zn-B and Cu-B due to organo-mineral complexes formation, maximizing specific surface area, lowering the electronegativity, originating positively charged functional groups, and thus improving the anion exchange capacity (AEC) comparing with O-B. In contrary, physicochemical characteristics of Mn-B was in similarity with those of O-B. Phosphate recovery by the functionalized biochar was much greater than that of the unfunctionalized forms (O-B and Mn-B). Precipitation was the dominant chemisorption mechanisms for phosphate sorption onto biochar compared to other mechanisms (ion exchange, electrostatic attraction and complexation with active functional groups). The exhausted biochar showed an ameliorating effect on the low water and nutrient supply potentials of sandy soil, and thus improved fresh biomass yield and nutritional status of maize seedlings with some restrictions on its high micronutrient content.