Use of response surface methodology for optimization of xylitol production by the new yeast strain Debaryomyces hansenii UFV-170

Optimisation of Propane Production from Hydrothermal Decarboxylation of Butyric Acid Using Pt/C Catalyst: Influence of Gaseous Reaction Atmospheres

The displacement and eventual replacement of fossil-derived fuel gases with biomass-derived alternatives can help the energy sector to achieve net zero by 2050. Decarboxylation of butyric acid, which can be obtained from biomass, can produce high yields of propane, a component of liquefied petroleum gases. The use of different gaseous reaction atmospheres of nitrogen, hydrogen, and compressed air during the catalytic hydrothermal conversion of butyric acid to propane have been investigated in a batch reactor within a temperature range of 200–350 °C. The experimental results were statistically evaluated to find the optimum conditions to produce propane via decarboxylation while minimizing other potential side reactions. The results revealed that nitrogen gas was the most appropriate atmosphere to control propane production under the test conditions between 250 °C and 300 °C, during which the highest hydrocarbon selectivity for propane of up to 97% was achieved. Below this temperature range, butyric acid conversion remained low under the three reaction atmospheres. Above 300 °C, competing reactions became more significant. Under compressed air atmosphere, oxidation to CO2 became dominant, and under nitrogen, thermal cracking of propane became significant, producing both ethane and methane as side products. Interestingly, under a hydrogen atmosphere, hydrogenolytic cracking propane became dominant, leading to multiple C–C bond cleavages to produce methane as the main side product at 350 °C.

Enhanced production of exopolysaccharides using industrial grade starch as sole carbon source

Industrial grade soluble corn starch was used directly and effectively as the fermentation substrate for microbial exopolysaccharides production. Bacillus subtilis mutant strain NJ308 grew with untreated starch raw material as the sole carbon source. The real-time PCR results demonstrated that up-regulated genes encoding N-acetylglucosaminyltransferase, mannosyltransferase, and N-acetylglucosamine-1-phosphate uridyltransferase were the key elements of B. subtilis mutant strain NJ308 for exopolysaccharides production from industrial grade starch. Subsequently, the culture conditions for B. subtilis NJ308 were optimized using Plackett-Burman design and central composite design methods, and the related key genes in the synthesis pathway of exopolysaccharides from the starch raw material were analyzed by real-time PCR. The maximum exopolysaccharides titration (3.41 g/L) was obtained when the initial starch concentration was 45 g/L. This corresponds to volumetric productivity values of 71.04 mg/L h.

Enhanced uridine diphosphate N-acetylglucosamine production using whole-cell catalysis

Uridine diphosphate N-acetylglucosamine (UDPAG) can be produced by chemical, enzymatic, chemoenzymatic, and fermentative methods. In this study, we used whole-cell catalysis method to produce UDPAG for the first time by Saccharomyces cerevisiae. In order to increase the ATP utilization efficiency and UDPAG conversion yield, the response surface methodology was applied to optimize the whole-cell catalytic conditions for UDPAG production. Firstly, effects of uridine 5'-monophosphate (5'-UMP), glucosamine, vitamin B1, glycerol, magnesium chloride, potassium chloride, temperature, sodium dihydrogen phosphate, sodium acetate, fructose, and pH on UDPAG production were evaluated by a fractional factorial design. Results showed that UDPAG production was mainly affected by sodium dihydrogen phosphate, temperature, and vitamin B1. Then, the concentrations of sodium dihydrogen phosphate and vitamin B1 and temperature were further investigated with a central composite design and response surface analysis. The cultivation conditions to obtain the optimal UDPAG production were determined: sodium dihydrogen phosphate, 31.2 g/L; temperature, 29 degrees C, and vitamin B1, 0.026 g/L. This optimization strategy led to an enhancement of UDPAG production from 2.51 to 4.25 g/L, yield from 44.6% to 75.6% based on the initial 5'-UMP concentration, and ATP utilization efficiency from 7.43% to 12.6%.