In the continuous systems, such as continuous beer fermentation, immobilized cells are kept inside the bioreactor for long periods of time. Thus an important factor in the design and performance of ...the immobilized yeast reactor is immobilized cell viability and physiology. Both the decreasing specific glucose consumption rate ( qim) and intracellular redox potential of the cells immobilized to spent grains during continuous cultivation in bubble‐column reactor implied alterations in cell physiology. It was hypothesized that the changes of the physiological state of the immobilized brewing yeast were due to the aging process to which the immobilized yeast are exposed in the continuous reactor. The amount of an actively growing fraction (Xactim) of the total immobilized biomass ( Xim) was subsequently estimated at approximately Xactim = 0.12 gIB gC−1 (IB = dry immobilized biomass, C = dry carrier). A mathematical model of the immobilized yeast biofilm growth on the surface of spent grain particles based on cell deposition (cell‐to‐carrier adhesion and cell‐to‐cell attachment), immobilized cell growth, and immobilized biomass detachment (cell outgrowth, biofilm abrasion) was formulated. The concept of the active fraction of immobilized biomass (Xactim) and the maximum attainable biomass load (Xmaxim) was included into the model. Since the average biofilm thickness was estimated at ca. 10 μm, the limitation of the diffusion of substrates inside the yeast biofilm could be neglected. The model successfully predicted the dynamics of the immobilized cell growth, maximum biomass load, free cell growth, and glucose consumption under constant hydrodynamic conditions in a bubble‐column reactor. Good agreement between model simulations and experimental data was achieved.
A suitable alternative to replace fossil fuels is the production of biodiesel from microalgae. They are among the most promising non-food-crop-based biomass feedstocks. In addition, microalgae have ...the potential to produce lipids with a high productivity such as two to three times more than what we can achieve with plants. Chlorella vulgaris has been a model organism, because of rapid biomass growth and potentially high oil content. The goal of this study was to develop sustainable processes that will increase productivity, maximize production efficiency and reduce production costs. Saline wastewater (SWW) represents a dairy industry waste that can be obtained at no cost whereas disposing the same according to regulations will incur significant costs. In this study, Chlorella vulgaris was examined for its ability to grow on saline wastewater from demineralization of cheese whey used as the basic component of waste culture medium (WCM). The composition of WCM was optimized (carbon, phosphor and nitrogen sources) by response surface methodology and evaluated statistically.
ABSTRACT
This work demonstrated the technological feasibility of the three‐phase airlift bioreactor (ALR) with brewing yeast immobilized on spent grains (a brewing by‐product) for continuous beer ...production. The optimum fermentation performance of the one stage immobilized cell bioreactor was achieved at residence times between 18–25 h (dilution rate 0.04–0.055 h−1) and was characterized by an apparent degree of attenuation in the range of 70–80%. The productivity of the system in terms of ethanol concentration in green beer (ca. 4.2%) was satisfactory. Although the diacetyl concentration in the young beer was high (0.32 mg L−1 at D = 0.04 h−1) it is speculated that the level could be reduced by cell growth control, aeration and temperature optimisation. The immobilized yeast fermentation in the ALR was shown to be robust in recovery after process upsets.
Fungal contamination poses a persistent challenge to industries, particularly in food, healthcare, and clinical sectors, due to the remarkable resilience of fungi in withstanding conventional control ...methods. In this context, our research delves into the comparative efficacy of UV radiation and non-thermal plasma (NTP) on key foodborne fungal contaminants -
Alternaria alternata
,
Aspergillus niger
,
Fusarium culmorum
, and
Fusarium graminearum
. The study examined the impact of varying doses of UV radiation on the asexual spores of all mentioned fungal strains. Simultaneously, the study compared the effects of UV radiation and NTP on the metabolic activity of cells after spore germination and their subsequent germination ability. The results revealed that UV-C radiation (254 nm) did not significantly suppress the metabolic activity of cells after spore germination. In contrast, NTP exhibited almost 100% effectiveness on both selected spores and their subsequent germination, except for
A. niger
. In the case of
A. niger
, the effectiveness of UV-C and NTP was nearly comparable, showing only a 35% decrease in metabolic activity after 48 hours of germination, while the other strains (
A. alternata
,
F. culmorum
,
F. graminearum
) exhibited a reduction of more than 95%. SEM images illustrate the morphological changes in structure of all tested spores after both treatments. This study addresses a crucial gap in existing literature, offering insights into the adaptation possibilities of treated cells and emphasizing the importance of considering exposure duration and nutrient conditions (introduction of fresh medium). The results highlighted the promising antimicrobial potential of NTP, especially for filamentous fungi, paving the way for enhanced sanitation processes with diverse applications.
The comparative efficacy of UV radiation and non-thermal plasma (NTP) on key foodborn fungal contaminants was studied. UV-C radiation (254 nm) did not significantly suppress the metabolic activity of cells are spore germination whereas NTP exhibited almost 100% effectiveness.
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