Selection of Saccharomyces cerevisiae strains for efficient very high gravity bio-ethanol fermentation processes

An optimized very high gravity (VHG) glucose medium supplemented with low cost nutrient sources was used to evaluate bio-ethanol production by 11 Saccharomyces cerevisiae strains. The industrial strains PE-2 and CA1185 exhibited the best overall fermentation performance, producing an ethanol titre of 19.2% (v/v) corresponding to a batch productivity of 2.5 g l-1 h-1, while the best laboratory strain (CEN.PK 113-7D) produced 17.5% (v/v) ethanol with a productivity of 1.7 g l-1 h-1. The results presented here emphasize the biodiversity found within S. cerevisiae species and that naturally adapted strains, such as PE-2 and CA1185, are likely to play a key role in facilitating the transition from laboratory technological breakthroughs to industrialscale bio-ethanol fermentations.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/BIO/66151/2006, SFRH/ BD/64776/2009, SFRH/BPD/44328/ 200

High intensity pulsed light as pre-treatment for enzymatic hydrolysis to modify whey protein

Introduction. Food allergies are hypersensitivity reactions mediated by immune mechanisms triggered by the presence of antigens –generally proteins- in food, such as those found in cows‘ milk. International guidelines recommend the use of extensively hydrolyzed formulas as alternative for children with Cow milk allergy. Strategies to reduce allergenicity of food proteins comprise treatments such as heating and hydrolysis. Non-thermal treatments are able to induce protein modifications similarly to thermal treatments; however less damage is produced by these innovative processing methods. Thus, high intensity pulsed light (HIPL) technology can be proposed alternatively to thermal treatments to assist on the reduction of food allergenicity. The aim of this work was to assess the effect of the use of HIPL treatment previous to enzymatic hydrolysis, applied to modify the antigenicity of target proteins, such as whey proteins. Materials and Methods. Experiments were carried out to verify the effectiveness of HIPL technology to accelerate protein hydrolysis reaction with a selected enzyme. The combined treatments are an alternative to induce further modification of proteins structure in order to affect their allergenic power. For this purpose, samples of whey solution were submitted to different HIPL-energy doses (0, 1, 3, 5, 8 and 12 J/cm2) at a fixed distance from the light source. Untreated sample was used as control. For the combined treatment, bromelain was added to HIPL pre-treated samples at an enzyme/ substrate ratio of 1/10 (w/w). Hydrolysis was carried out for 0, 5, 10, 20, or 30 min. Results. Concerning the efficiency of HIPL treatment to induce protein unfolding, the highest exposure of free SH groups took place upon the highest energy doses. When HIPL treatment was combined with enzymatic hydrolysis, a raise in the degree of hydrolysis was observed, particularly at the highest energy levels tested. Conclusions. Results obtained in the present work suggest that, even if an increased antigenicity potentially occurs due to the exposure of hidden linear epitopes upon the unfolding induced by the non-thermal treatment assayed, further peptide bonds cleavage also take place after hydrolysis. This effect could change whey proteins antigens, and thus its antigenic power. Although further studies are required these preliminary result is promising

High Voltage Electrical Discharges as an Alternative Extraction Process of Phenolic and Volatile Compounds fromWild Thyme (Thymus serpyllum L.): In Silico and Experimental Approaches for Solubility Assessment

The objective of this study was to evaluate the potential of green solvents for extractions of bioactive compounds (BACs) and essential oils from wild thyme (Thymus serpyllum L.) using theoretical and experimental procedures. Theoretical prediction was assessed by Hansen solubility parameters (HSPs) and conductor-like screening model for realistic solvents (COSMO-RS), to predict the most suitable solvents for extraction of BACs. An experimental procedure was performed by nonthermal technology high voltage electrical discharge (HVED) and it was compared with modified conventional extraction (CE). Obtained extracts were analyzed for chemical and physical changes during the treatment. Theoretical results for solution of BACs in ethanol and water, as green solvents, were confirmed by experimental results, while more accurate data was given by COSMO-RS assessment than HSPs. Results confirmed high potential of HVED for extraction of BACs and volatile compounds from wild thyme, in average, 2.03 times higher yield of extraction in terms of total phenolic content was found compared to CE. The main phenolic compound found in wild thyme extracts was rosmarinic acid, while the predominant volatile compound was carvacrol. Obtained extracts are considered safe and high-quality source reach in BACs that could be further used in functional food production

Evaluating the influence of operational parameters of pulsed light on wine related yeasts: focus on inter- and intra-specific variability sensitivity

In oenology, there is a growing demand by consumers for wines produced with less inputs (such as sulphite, frequently used for microbial control). Emerging control methods for managing microorganisms in wine are widely studied. In this study, the efficiency of pulsed light (PL) treatment was investigated. A drop-platted system was used to evaluate the impact of three PL operational parameters: the fluence per flash, the total fluence and the flash frequency. Fluence per flash appeared to be a key parameter prior to total fluence, thus demonstrating the importance of the effect of peak voltage during PL treatments. The efficiency of PL treatment was assessed on 198 strains distributed amongst fourteen yeast species related to wine environment, and an important variability in PL response was observed. Brettanomyces bruxellensis strains were strongly sensitive to PL, with intraspecific variation. PL was then applied to red wines inoculated with 9 strains of B. bruxellensis, Saccharomyces cerevisiae and Lachancea thermotolerans. Results confirmed interspecific response variability and a higher sensitivity of B. bruxellensis species to PL. Wine treatments with a total fluence of 22.8 J cm-2 resulted in more than 6 log reduction for different B. bruxellensis strains. These results highlight the potential of PL for wine microbial stabilization

Guidelines on reporting treatment conditions for emerging technologies in food processing

In the last decades, different non-thermal and thermal technologies have been developed for food processing. However, in many cases, it is not clear which experimental parameters must be reported to guarantee the experiments’ reproducibility and provide the food industry a straightforward way to scale-up these technologies. Since reproducibility is one of the most important science features, the current work aims to improve the reproducibility of studies on emerging technologies for food processing by providing guidelines on reporting treatment conditions of thermal and non-thermal technologies. Infrared heating, microwave heating, ohmic heating and radiofrequency heating are addressed as advanced thermal technologies and isostatic high pressure, ultra-high-pressure homogenization sterilization, high-pressure homogenization, microfluidization, irradiation, plasma technologies, power ultrasound, pressure change technology, pulsed electric fields, pulsed light and supercritical CO2 are approached as non-thermal technologies. Finally, growing points and perspectives are highlighted