Edible pullulan enhanced water-soluble keratin with improved sizing performance for sustainable textile industry

Feather keratin from waste feather has become an attractive target to replace petroleum-based Poly (vinyl alcohol) sizes due to its easy film-forming ability, excellent adhesive property, biodegradability and low cost. However, poor water-solubility and brittleness of pure keratin films have become the bottlenecks and restricted the application of keratin as sizing agents. Therefore, water-soluble keratin was extracted by the reduction-preservation method and enhanced by saccharides in aqueous system to obtain all-green keratin-based slurry. The results showed that the keratin-based slurry exhibited improved sizing performance in the order of sucrose ≤ glucose ≤ pullulan by the moderate Maillard reaction. Among them, the fabricated pullulan-keratin sizes films had 27.86 %, 2684.08 % and 2911.31 % increment in tensile strength, elongation and work of facture compared with pure keratin sizes films. Besides, the addition of pullulan and subsequently moderate Maillard reaction improved the thermo-tenacity of keratin-based sizes, which was expected to tackle with the brittleness of pure keratin size films. In addition, novel pullulan-keratin sizes had good sizing performance and high desizing efficiency to cotton, cotton/polyester and polyester yarns and fabrics. Successful utilization of pullulan-keratin sizes will bring opportunities for high value utilization of waste feather and promote the green and low-carbon development of textile industry.

Oxygen mass transfer enhancement by activated carbon particles in xylose fermentation media

In this work, the effect of activated carbon particles on the production of xylonic acid from xylose by Gluconobacter oxydans in a stirred tank bioreactor was investigated. The enhancement of the oxygen transfer coefficient by activated carbon particles was experimentally evaluated under different solids volume fractions, agitation and aeration rates conditions. The experimental conditions optimized by response surface methodology (agitation speed 800 rpm, aeration rate 7 L min^-1, and activated carbon 0.002%) showed a maximum oxygen transfer coefficient of 520.7 h^-1, 40.4% higher than the control runs without activated carbon particles. Under the maximum oxygen transfer coefficient condition, the xylonic acid titer reached 108.2 g/L with a volumetric productivity of 13.53 g L^-1 h^-1 and a specific productivity of 6.52 g/g_x/h. In conclusion, the addition of activated carbon particles effectively enhanced the oxygen mass transfer rate. These results demonstrate that activated carbon particles enhanced cultivation for xylonic acid production an inexpensive and attractive alternative.

Optimization of Specific Productivity for Xylonic Acid Production by Gluconobacter oxydans Using Response Surface Methodology

Large amounts of xylose cannot be efficiently metabolized and fermented due to strain limitations in lignocellulosic biorefinery. The conversion of xylose into high value chemicals can help to reduce the cost of commercialization. Therefore, xylonic acid with potential value in the construction industry offers a valuable alternative for xylose biorefinery. However, low productivity is the main challenge for xylonic acid fermentation. This study investigated the effect of three reaction parameters (agitation, aeration, and biomass concentration) on xylose acid production and optimized the key process parameters using response surface methodology The second order polynomial model was able to fit the experimental data by using multiple regression analysis. The maximum specific productivity was achieved with a value of 6.64 ± 0.20 g g_x⁻¹ h⁻¹ at the optimal process parameters (agitation speed 728 rpm, aeration rate 7 L min⁻¹, and biomass concentration 1.11 g L⁻¹). These results may help to improve the production efficiency during xylose acid biotransformation from xylose.

Understanding the Effect of Impeller Configurations on Pullulan Production by Aureobasidium Pullulans RBF 4A3

Mass transfer is one of the most important factors involved in viscous fermentation processes, like production of pullulan. Impellers play a crucial role in maintaining homogeneity and better mass transfer conditions during the fermentation process. The present study attempted to evaluate the efficiency of impellers with diverse configurations during pullulan fermentation. Initially, the mass transfer coefficients of 10 selected impellers were evaluated in an aqueous system. Among these, three impellers, namely, single helical ribbon, Rushton turbine, and Smith turbine impellers, were found to be more efficient and were further employed in the pullulan fermentation process. The results suggested that the single helical ribbon impeller was able to provide 24% higher pullulan production as compared to the Rushton turbine and Smith turbine impellers. The single helical ribbon was able to maintain the critical demand of dissolved oxygen in fermentation broth. Therefore, it may be commented that the single helical ribbon impeller configuration is suitable for higher production of pullulan during the fermentation process.

Toward understanding the key enzymes involved in β-poly (L-malic acid) biosynthesis by Aureobasidium pullulans ipe-1

β-poly (L-malic acid) (PMLA) is a biopolyester which has attracted industrial interest for its potential application in medicine and other industries. A high dissolved oxygen concentration (DO) was beneficial for PMLA production, while the mechanisms of DO in PMLA biosynthesis by Aureobasidium pullulans are still poorly understood. In this work, the amount of PMLA was first compared when A. pullulans ipe-1 were cultured under a high DO level (70% saturation) and a low DO level (10% saturation). Meanwhile, the key enzymes involved in different pathways of the precursor L-malic acid biosynthesis were studied. The results revealed that the activities of glucose-6-phosphate dehydrogenase (G6PDH) and phosphoenolpyruvate carboxylase (PEPC) were positively correlated with cell growth and PMLA production, while the activities of phosphofructokinases (PFK), pyruvic carboxylase (PC) and citrate synthetase (CS) did no show such correlations. It indicated that the Pentose Phosphate Pathway (PPP) may play a vital role in cell growth and PMLA biosynthesis. Moreover, the precursor L-malic acid for PMLA biosynthesis was mainly biosynthesized through phosphoenolpyruvic acid (PEP) via oxaloacetate catalyzed by PEPC. It was also found that low concentration of sodium fluoride (NaF) might impel carbon flux flow to the oxaloacetate through PEP, but inhibit the flux to the oxaloacetate via pyruvic acid.

Why sucrose is the most suitable substrate for pullulan fermentation by Aureobasidium pullulans CGMCC1234?

This paper studies the metabolic pathway of sucrose in pullulan fermentation by Aureobasidium pullulans. Because of its high pullulan production, sucrose proved to be the best carbon source for pullulan synthesis by A. pullulans CGMCC1234 (36.3g/L). Compared to other carbon sources, A. pullulans cells reached the stationary phase more quickly in the presence of sucrose. The specific sugar types and concentrations occurring during pullulan fermentation were detected using High Performance Liquid Chromatography (HPLC). HPLC results revealed that sucrose did not simply break down into glucose and fructose in the medium employed. Kestose (22.69g/L) also accumulated during early stages of fermentation (24h), which reduced the osmotic pressure of the extracellular fluid and diminished the inhibition of cell growth and pullulan production. β-Fructofuranosidase activity strongly depended on the carbon source. Sucrose was the best inducer of β-fructofuranosidase production. However, β-fructofuranosidase production did not directly and/or proportionally correlate with the growth of A. pullulans cells.