Optimization of a fermented pumpkin-based beverage to improve Lactobacillus mali survival and-glucosidase inhibitory activity:A response surface methodology approach

The aim of this research was to develop an optimum fermentation and composition model for a new fermented pumpkin-based beverage with high probiotic survival and-glucosidase inhibitory activity.Relationship between fermentation temperature,inoculum and ingredient concentration with response variables(fermentation time at the fermentation endpoint pH 4.5,survival rate of Lactobacillus mali K8 in pumpkin-based beverage treated with simulated gastrointestinal tract enzyme fluids,-glucosidase inhibitory activity and sensory overall acceptability after 4 weeks of refrigerated storage)was investigated using response surface methodology.Optimal formulation was obtained at an approximation of 40%pumpkin puree concentration,8 Log CFU/mL inoculum and at 35℃.The product derived from this optimum formula reached the fermentation endpoint after 28.34±0.10 h and the quality change during 4 weeks storage was studied.The product achieved 88.56±0.67%of L.mali survival after treatment with simulated gastric and intestinal juices;demonstrated 95.89±0.30% α-glucosidase inhibitory activity,as well as scored 6.99±0.40 on sensory overall acceptability after 4 weeks of storage.These findings illustrated that the model is effective in improving probiotic survival and α-glucosidase inhibitory activity with excellent sensory acceptability,thus may offer a dietary means for the management of hyperglycaemia.

Towards Biorefinery Production of Microalgal Biofuels and Bioproducts: Production of Acetic Acid from the Fermentation of <i>Chlorella</i>sp. and <i>Tetraselmis suecica</i>Hydrolysates

Successful commercialization of microalgal bio-industry requires the design of an integrated microalgal biorefinery system that facilitates the co-production of biofuels, high-value products and industrial chemicals from the biomass. In this study, we investigated the use of sugar hydrolysate obtained from enzymatic saccharification of microalgal biomass (Chlorella sp. and T. suecica) as fermentation feedstock to produce industrially important chemicals, in particular acetic acid and butyric acid. By using hydrolysate with low sugar content as substrate for the anaerobic fermentation (1.5 - 2.4 g/L), we were able to prevent the bacterium C. saccharoperbutylacetonicum from activating its solventogenesis pathway. As a result, the fermentation process generated a product stream that was dominated by organic acids (acetic acid and butyric acid) rather than solvents (butanol, ethanol and acetone). Acetic acid constituted up to 92 wt% of Chlorella’s fermentation products and 80 wt% of T. suecica’s fermentation products. For T. suecica, the fermentation consumed almost all of the sugar available in the hydrolysate (up to 92% of initial sugar) and produced a reasonable yield of fermentation products (0.08 g fermentation products/g sugar). The Gompertz equation was successfully used to predict the formation kinetics of acetic acid and other fermentation products across both species. The results in the study demonstrate the production of industrially important chemicals, such as acetic acid and butyric acid, from the fermentation of microalgal sugar. The process described in the study can potentially be used as a value-adding step to generate biochemicals from cell debris in an integrated microalgal biorefinery system.

An analysis of quantitative PCR reliability through replicates using the C_(t)method

There is considerable interest in quantitatively measuring nucleic acids from single cells to small populations. The most commonly employed laboratory method is the real-time polymerase chain reaction (PCR) analyzed with the crossing point or crossing threshold (Ct) method. Utilizing a multiwell plate reader we have performed hundreds of replicate reactions each at a set of initial conditions whose initial number of copies span a concentration range of ten orders of magnitude. The resultant Ct value distributions are analyzed with standard and novel statistical techniques to assess the variability/reliability of the PCR process. Our analysis supports the following conclusions. Given sufficient replicates, the mean and/or median Ct values are statistically distinguishable and can be rank ordered across ten orders of magnitude in initial template concentration. As expected, the variances in the Ct distributions grow as the number of initial copies declines to 1. We demonstrate that these variances are large enough to confound quantitative classi?cation of the initial condition at low template concentrations. The data indicate that a misclassi?cation transition is centered around 3000 initial copies of template DNA and that the transition region correlates with independent data on the thermal wear of the TAQ polymerase enzyme. We provide data that indicate that an alternative endpoint detection strategy based on the theory of well mixing and plate ?lling statistics is accurate below the mis- classi?cation transition where the real time method becomes unreliable.