A stoichiometry-based model for the fed-batch culture of the recombinant bacterium Bacillus subtilis ATCC 6051a, producing extracellular alpha-amylase as a desirable product and proteases as undesirable products, was developed and verified. The model was then used for optimizing the feeding schedule in fed-batch culture. To handle higher-order model equations (14 state variables), an optimization methodology for the dual-enzyme system is proposed by integrating Pontryagin's optimum principle with fermentation measurements. Markov chain Monte Carlo (MCMC) procedures were appropriate for model parameter and decision variable estimation by using a priori parameter distributions reflecting the experimental results. Using a simplified Metropolis-Hastings algorithm, the specific productivity of alpha-amylase was maximized and the optimum path was confirmed by experimentation. The optimization process predicted a further 14% improvement of alpha-amylase productivity that could not be realized because of the onset of sporulation. Among the decision variables, the switching time from batch to fed-batch operation (t(s)) was the most sensitive decision variable.

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The objective of this study was to investigate the effect of starter culture addition on proteolysis of Thai fermented sausages. Sausages inoculated with six different external starter cultures-Pediococcus pentosaceous, Pediococcus acidilactici, Weissella cibaria, Lactobacillus plantarum, Lactobacillus pentosus, and Lactobacillus sakei-were compared with naturally fermented sausages. The results of microbiological analysis indicated that the dominance of lactic acid bacteria (LAB) could inhibit the growth of pathogens and spoilage. Proteolysis was observed during fermentation by the reduction of myofibrillar and sarcoplasmic proteins and the increase in nonprotein nitrogen (NPN) and total free amino acids. The highest increase in concentration of NPN and free amino acids was obtained from sausages inoculated with LAB. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed a similar pattern of proteolysis of sarcoplasmic proteins in all sausages, while that of the inoculated sausages with L. plantarum, L. pentsus, and L. sakei exhibited increased degradation of myofibrillar protein bands at 200 and 45 kDa.

Improvement of the conventional sausage fermentation process was investigated by introducing six different external starter cultures including Pediococcus pentosaceous, Pediococcus acidilactici, Weissella cibaria, Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus sakei. The results of microbiological analysis indicated that the dominance of lactic acid bacteria could inhibit the growth of pathogens and spoilage. Sausages inoculated with starters exhibited lower pH (pH = 4.51–4.67) than the uninoculated control. The decrease of pH was attributed to organic acid, mainly by lactic acid production. The initial rate of lactic acid production in sausages inoculated with starter cultures was higher than the control. P. acidilactici showed the highest initial rate of lactic acid production (4.45 × 10−2 g/100g·h) and lactic acid yield (0.89), while the initial rate of lactic acid production and lactic acid yield were 2.66 × 10−2 g/100g·h and 0.63, respectively, in control experiments. The sausage inoculated with P. acidilactici recorded the highest scores for overall acceptability. PRACTICAL APPLICATIONS The fermentation of traditional fermented sausages is caused by natural, wild‐type lactic acid bacteria such as lactobacilli and pediococci that originate from the row meat, or the process apparatus or the environment and takes 2–3 days at room temperature. The use of starter cultures in sausages production has improved food safety and to standardize product properties such as flavor compound, lactic acid, color and texture. In addition, the sensory of sausages inoculated with starter cultures are more acceptable than uninoculated sausages.

This study aimed at investigating the in uence of commercial transfection reagents (Prime-Fect, Leu-Fect A, and Leu-Fect C) complexed with different siRNAs (CDC20, HSP90, Mcl-1 and Survivin) in MDA-MB-436 breast cancer cells and the impact of incorporating an anionic additive, Trans-Booster, for improving in vitro gene silencing and delivery e ciency. Gene silencing was quantitatively analyzed by real-time RT-PCR while cell proliferation and siRNA uptake were evaluated by the MTT assay and ow cytometry, respectively. Amongst the investigated siRNAs and transfection reagents, Mcl-1/Prime-Fect complexes showed the highest inhibition of cell viability and most effective siRNA delivery. The effect of various formulations on transfection e ciency showed that a anionic additive with 1:1 ratio with siRNA was optimal achieving the lowest cell viability compared to untreated cells and negative control siRNA treatment (p<0.05). Furthermore, the combination of Mcl-1 and survivin siRNA suppressed the growth of MDA-MB-436 cells more effectively than treatment with the single siRNAs and resulted in a cell viability as low as ~20% (vs. non-treated cells). This aligned well with the induction of apoptosis as analyzed by ow cytometry, which revealed higher apoptotic cells with the combination treatment group. We conclude that commercial transfection reagents formulated with Mcl-1/Survivin siRNA combination could serve as a potent anti-proliferation agent in treatment of breast cancers.