Acid soaking followed by steam flash-explosion pretreatment to enhance saccharification of rice husk for poly(3-hydroxybutyrate) production

Preparation of xylooligosaccharides from rice husks and their structural characterization, antioxidant activity, and probiotic properties

Rice husks are rich in xylan, which can be hydrolyzed by xylanase to form xylooligosaccharides (XOS). XOS are a functional oligosaccharide such as improving gut microbiota and antioxidant properties. In this study, the structure and functional characteristics of XOS were studied. The optimal xylanase hydrolysis conditions through response surface methodology (RSM) were: xylanase dosage of 3000 U/g, hydrolysis time of 3 h, hydrolysis temperature of 50 °C. Under this condition, the yield of XOS was 150.9 mg/g. The TG-DTG curve showed that XOS began to decompose at around 200 °C. When the concentration of XOS reached 1.0 g/L, the clearance rate of DPPH reached 65.76 %, and the scavenging rate of OH reached 62.10 %, while the clearance rate of ABTS free radicals reached 97.70 %, which was equivalent to the clearance rate of VC. XOS had a proliferative effect on four probiotics: Lactobacillus plantarum, Lactobacillus brucelli, Lactobacillus acidophilus, and Lactobacillus rhamnosus. However, the further experiments are needed to explore the improvement effect of XOS on human gut microbiota, laying a foundation for the effective utilization of XOS. XOS have a wide range of sources, low price, and broad development prospects. The reasonable utilization of XOS can bring greater economic benefits.

Polyhydroxy butyrate biosynthesis by Azotobacter chroococcum MTCC 3858 through groundnut shell as lignocellulosic feedstock using resource surface methodology

This work appraises the prospect of utilising groundnut shell hydrolysate as a feedstock used for PHB biosynthesis by Azotobacter chroococcum MTCC 3853 under SMF conditions. Sugar reduction: untreated and pretreated 20% H₂SO₄ (39.46 g/l and 62.96 g/l, respectively), untreated and enzymatic hydrolysis (142.35 mg/g and 568.94 mg/g). The RSM-CCD optimization method was used to generate augment PHB biosynthesis from groundnut shell hydrolysate (30 g/l), ammonium sulphate (1.5 g/l), ammonium chloride (1.5 g/l), peptone (1.5 g/l), pH 7, 30 °C, and a 48 h incubation time. The most convincing factors (p < 0.0001), coefficient R² values of biomass 0.9110 and PHB yield 0.9261, PHB production, highest biomass (17.23 g/l), PHB Yield(11.46 g/l), and 66.51 (wt% DCW) values were recorded. The control (untreated GN) PHB yield value of 2.86 g/l increased up to fourfold in pretreated GN. TGA results in a melting range in the peak perceived at 270.55 °C and a DSC peak range of 172.17 °C, correspondingly. According to the results, it furnishes an efficient agricultural waste executive approach by diminishing the production expenditure. It reinforces the production of PHB, thereby shrinking our reliance on fossil fuel-based plastics.

A novel chitinous nanoparticles prepared and characterized with black soldier fly (Hermetia illucens L.) using steam flash explosion treatment

This is the first report of the use of steam flash explosion (SFE) to prepare chitinous nanoparticles from black soldier fly (BSF). SFE treatment was performed at a steam pressure of 0.45 to 1.60 MPa with a holding time of 60 s. As the pressure increased, the particle size of the chitinous particles decreased. Under SFE at 1.60 MPa, chitinous nanoparticles with sizes ranging from 59 to 162 nm were produced. SEM, AFM, Raman spectroscopy, FT-IR spectroscopy, ¹H NMR, TGA, and DSC were used to characterize the BSF chitin materials. It was demonstrated that SFE treatment deacetylated chitin to obtain chitosan with 91.24 % deacetylation. In addition, the polymer backbone was maintained, and the degree of polymerization of chitosan nanoparticles was reduced. The activity of the cationic groups of chitosan nanoparticles was improved, thereby enhancing the temperature sensitivity of the polymeric material. It can be concluded that the SFE one-step processing method is a simple and efficient way to prepare homogeneous biomaterial nanoparticles. This study has implications for the development of chitosan nanomaterials for biomedical applications.

Biotransformation of d-Xylose-Rich Rice Husk Hydrolysate by a Rice Paddy Soil Bacterium, Priestia sp. Strain JY310, to Low Molecular Weight Poly(3-hydroxybutyrate)

Poly(3-hydroxybutyrate) (PHB) is a versatile thermoplastic with superior biodegradability and biocompatibility that is intracellularly accumulated by numerous bacterial and archaeal species. Priestia sp. strain JY310 that was able to efficiently biotransform reducing sugars in d-xylose-rich rice husk hydrolysate (reducing sugar_RHH) to PHB was isolated from the soil of a rice paddy. Reducing sugar_RHH including 12.5% d-glucose, 75.3% d-xylose, and 12.2% d-arabinose was simply prepared using thermochemical hydrolysis of 3% H₂SO₄-treated rice husk for 15 min at 121 °C. When cultured with 20 g/L reducing sugar_RHH under optimized culture conditions in a batch bioreactor, Priestia sp. strain JY310 could produce PHB homopolymer up to 50.4% of cell dry weight (6.2 g/L). The melting temperature, heat of fusion, and thermal decomposition temperature of PHB were determined to be 167.9 °C, 92.1 J/g, and 268.1 °C, respectively. The number average and weight average molecular weights of PHB with a broad polydispersity index value (4.73) were estimated to be approximately 16.2 and 76.8 kg/mol, respectively. The findings of the present study suggest that Priestia sp. strain JY310 can be exploited as a good candidate for the low-cost production of low molecular weight PHB with improved biodegradability and reduced brittleness from inexpensive agricultural waste hydrolysates.

Development of a purification process via crystallization of xylitol produced for bioprocess using a hemicellulosic hydrolysate from the cashew apple bagasse as feedstock

Xylitol was biotechnologically produced by Kluyveromyces marxianus ATCC36907 using the hemicellulosic hydrolysate of the cashew apple bagasse (CABHH). Sequentially, the present study investigated the recovery and purification of xylitol evaluating different antisolvents [ethanol, isopropanol and the ionic liquid 2-hydroxyl-ethylammonium acetate (2-HEAA)], their proportion in the medium (10-90% v/v), and their cooling rate (V_C 0.25-0.50 °C/min). These processes were contrasted with the crystallization process of commercial xylitol. This study is the first to assess xylitol crystallization using a protic ionic liquid. The hydrolysate obtained from a mild treatment with sulfuric acid contained mainly glucose and xylose at concentrations of 15.7 g/L and 11.9 g/L, respectively. With this bioprocess, a maximum xylitol production of 4.5 g/L was achieved. The performance of the investigated antisolvents was similar in all conditions evaluated in the crystallization process of the commercial xylitol, with no significant difference in yields. For the crystallization processes of the produced xylitol, the best conditions were: 50% (v/v) isopropanol as antisolvent, cooling rate of 0.5 °C/min, with a secondary nucleation of yield and purity of 69.7% and 84.8%, respectively. Under the same linear cooling rate, using ethanol, isopropanol or the protic ionic liquid 2-hydroxyl-ethylammonium acetate (2-HEAA), crystallization did not occur, probably due to the presence of carbohydrates not metabolized by the yeast in the broth, which influences the solubility curve of xylitol. With the results of this work, a possible economical and environmentally friendly process of recovery and purification of xylitol from CABHH could be proposed.

Development of a purification process via crystallization of xylitol produced for bioprocess using a hemicellulosic hydrolysate from the cashew apple bagasse as feedstock

Xylitol was biotechnologically produced by Kluyveromyces marxianus ATCC36907 using the hemicellulosic hydrolysate of the cashew apple bagasse (CABHH). Sequentially, the present study investigated the recovery and purification of xylitol evaluating different antisolvents [ethanol, isopropanol and the ionic liquid 2-hydroxyl-ethylammonium acetate (2-HEAA)], their proportion in the medium (10-90% v/v), and their cooling rate (V_C 0.25-0.50 °C/min). These processes were contrasted with the crystallization process of commercial xylitol. This study is the first to assess xylitol crystallization using a protic ionic liquid. The hydrolysate obtained from a mild treatment with sulfuric acid contained mainly glucose and xylose at concentrations of 15.7 g/L and 11.9 g/L, respectively. With this bioprocess, a maximum xylitol production of 4.5 g/L was achieved. The performance of the investigated antisolvents was similar in all conditions evaluated in the crystallization process of the commercial xylitol, with no significant difference in yields. For the crystallization processes of the produced xylitol, the best conditions were: 50% (v/v) isopropanol as antisolvent, cooling rate of 0.5 °C/min, with a secondary nucleation of yield and purity of 69.7% and 84.8%, respectively. Under the same linear cooling rate, using ethanol, isopropanol or the protic ionic liquid 2-hydroxyl-ethylammonium acetate (2-HEAA), crystallization did not occur, probably due to the presence of carbohydrates not metabolized by the yeast in the broth, which influences the solubility curve of xylitol. With the results of this work, a possible economical and environmentally friendly process of recovery and purification of xylitol from CABHH could be proposed.

Charge-oriented strategies of tunable substrate affinity based on cellulase and biomass for improving in situ saccharification: A review

The intrinsic recalcitrance of lignocellulosic biomass makes it resistant to enzymatic hydrolysis. The electron-rich surface of the lignin and cellulose-alike structure of hemicellulose competitively absorb the cellulase. Thus, modifying the surface charge on biomass components to alter cellulase affinity is an urgent requisite. Developing charge tunable cellulase will alter substrate affinity. Also, charge-based immobilization generates controllable substrate affinity. Within immobilized cellulase involved in situ biomass saccharification, charge effects made a crucial contribution. In addition to affecting the interaction between immobilized cellulase and biomass, charge exerts an impact on cellulase to immobilize the materials, further investigation is essential. This study aims to review the charge effects on the cellulase affinity in biomass saccharification, strategies of charge tunable cellulase, and immobilized cellulase, thereby explaining the role of electrostatic interaction. In terms of electrostatic behavior, the pathways and plans to improve in situ biomass saccharification seem to be promising.