Physiological tests for yeast brewery cells immobilized on modified chamotte carrier

Utilization of Corncob as an Immobilization Matrix for a Xylanolytic Yeast Strain

Immobilization of microbial cells for the production of industrially important enzymes has been reported to offer the advantages of recyclability, higher yields and cost effectiveness. The search for an appropriate matrix that is affordable and easy to prepare is a significant topic in microbial biotechnology. Here, an abundant type of agro-industrial waste-corncob-was utilized as an immobilization matrix for the production of xylanase from an indigenous yeast strain, Saccharomyces cerevisiae MK-157. This is the first report describing xylanase production from immobilized S. cerevisiae. To render the corncob matrix more porous, alkaline pretreatment was undertaken and yeast cells were immobilized on the matrix by cultivating at 30 °C for 48 h in Sabouraud dextrose broth. After incubation, the immobilized matrix was transferred to mineral salt medium containing 1% xylan and incubated at 30 °C for 24 h. Xylanase production was determined in cell-free culture supernatant and the matrix was recycled for up to seven cycles. Moreover, xylanase-mediated saccharification was carried out using sugarcane bagasse as a substrate and the release of reducing sugars was monitored. The results showed that the immobilized yeast produced 4.97 IU mL-1 xylanase in the first production cycle, indicating a >tenfold increase compared to the free cells. Xylanase production further increased to its maximum levels (9.23 IU mL-1) in the fourth production cycle. Nonetheless, the cells retained 100% productivity for up to seven cycles. The volumetric and specific productivity of xylanase were also the highest in the fourth cycle. Scanning electron microscopy images revealed the rough surface of the untreated corncob, which became more porous after alkaline pretreatment. Immobilized yeast cells were also visible on the corncob pieces. The saccharification of a natural resource-sugarcane bagasse-using xylanase preparation yielded 26 mg L-1 of reducing sugars. Therefore, it can be concluded that yeast strains can yield sufficient quantities of xylanase, allowing possible biotechnological applications. Moreover, corncob can serve as a cost-effective matrix for industrially important yeast strains.

A Survey on Detection of Plastic-Related Chemicals in Beer Packaged in PET Using FT-IR Technology

The emerging consciousness on nano- and microplastics in our environment raises questions on how to reduce and minimize its influence on human health. PET (polyethylene terephthalate) packaging is gaining popularity, and many traditional products end up in such packaging (vinegar, wine, beer). Currently, it is very hard to quantify the number of particles and their exact composition, but semi-quantitative techniques such as FT-IR (Fourier Transform Infrared Spectrophotometry) can give us an insight into the chemical composition of plastic bits in foods and beverages. Nowadays, beer is packed in PET packaging, since it provides a cheaper packaging material compared to glass and since it is safe to use at public manifestations, contrary to glass bottles, while providing a reasonable barrier for gas permeation (O2 and CO2). The aim of this paper was to provide a short overview of FT-IR-detected compounds in PET-packaged beer samples. The results indicate that many compounds can be found in beer, but those that were most commonly found in our research were β-cyclodextrin and L(-)-glyceraldehyde unnatural forms, two compounds designated as plastic-related compounds.

Increased production of chitinase by a Paenibacillus illinoisensis isolated from Brazilian coastal soil when immobilized in alginate beads

The accumulation of chitin waste from the seafood industry is a serious environmental problem. However, this residue can be degraded by chitinases and its subproducts, such as chitosan, economically exploited. In this study, a chitinase producer bacteria, identified as Paenibacillus illinoisensis, was isolated from the Brazilian coastal city of Terra de Areia - Rio Grande Do Sul (RS) and was immobilized within alginate beads to evaluate its chitinase production. The alginate beads containing cells presented an average size of 4 mm, 99% of immobilization efficiency and increased the enzymatic activity in 40.71% compared to the free cells. The biomass during enzymatic production increased 62.01% and the total cells leaked from the alginate beads corresponded to 6.46% after 96 h. Immobilized cells were reused in a sequential batch system and remained stable for production for up to four 96-h cycles, decreasing only 21.04% of the initial activity at the end of the fourth cycle. Therefore, the methodology used for cell immobilization resulted in adequate beads to maintain cell viability during the enzymatic production, increasing enzymatic activity, showing low cell leakage from the support and appropriate recyclable capacity.

Incorporating Transcriptomic-Metabolomic analysis reveal the effect of ultrasound on ethanol production in Saccharomyces Cerevisiae

This study reports an enhancement of ethanol yield in Saccharomyces cerevisiae with low-intensity ultrasonic irradiation using fixed mode frequency generated by a self-developed six-frequencies (20, 23, 25, 28, 33, 40 kHz) ultrasonic device in our group. After sonication treatment, the ethanol production potential was determined. Under the optimal conditions of ultrasonic treatment (ultrasonic frequency 28 kHz, power density 180 W/L, and treatment time 24 h), the maximum ethanol yield increased by 34.87% compared to the control. Transcriptome sequencing showed that the ultrasonic treatment had expressional regulations on genes involved in pyruvate metabolism, glycolysis, pentose phosphate pathway, glucose transport, and reducing power production. The quantitative real-time polymerase chain reaction (qRT-PCR) further confirmed the changes in gene expression (up- or down-regulation). Metabolomics revealed that ultrasonic treatments increased intracellular glucose and nicotinamide adenine dinucleotide (NADH) contents, which are key metabolites for ethanol synthesis. Besides, ultrasonic treatments decreased the acetate and its derivatives resulting in lowered reverse consumption of pyruvate and thus promoted ethanol synthesis. These changes in gene expression and metabolites content might be the main reason why the ethanol yield in Saccharomyces cerevisiae increased after ultrasonic irradiation.

Two layered strategy for cost effective production of pectinase: immobilization of yeast and utilization of crude substrate

The wide scale application of pectinase is generally hindered by high cost of the enzyme production. In this work, a two dimensional strategy was adopted to reduce cost of pectinase production by Geotrichum candidum AA15. The strain was immobilized in alginate beads. The optimum concentration for bead formation was found to be 3.5% of sodium alginate (NA) with 4% calcium chloride (CaCl₂). Such immobilized cells retained the ability to produce 0.115 IU mL^-1 of pectinase for up to 6^th production cycle in citrus pectin containing medium while free cells produced only 0.046 IU mL^-1 of pectinase. For the cultivation of immobilized cells on orange peels (OP), a combination of 4.5% NA and 4% CaCl₂ was found effective to prepare beads. Geotrichum candidum AA15 produced 0.220 IU mL^-1 pectinase by fermenting OP as a substrate for up to 3^rd production cycle. The results revealed that the process of immobilization can be used as a promising strategy in combination with the use of naturally available waste biomass.

Novel microencapsulated yeast for the primary fermentation of green beer: kinetic behavior, volatiles and sensory profile

The development of innovative and more cost-effective approaches of making beer throughout continuous fermentation process remains a challenging problem, which is worthy of serious exploration. The current work focuses on the application of a commercial brewing yeast (S. cerevisiae Nottingham Ale), entrapped into chitosan-calcium alginate double layer microcapsules, for the production of a Pale Ale beer. During the primary alcoholic fermentation, the consumption rate of fermentable brewing sugars and dissolved O₂, estimated by the Gompertz equation, was halved in the beer obtained by encapsulated yeast in comparison with the free cell. The physical-chemical parameters of beer (i.e. pH, alcohol content, color and bitterness) were not remarkably affected by the different yeast-inoculating form. However, the volatile profiles identified by means of HS-SPME-GC-MS analysis, significantly differed in terms of terpenes, esters and alcohols content, thus proving that the yeast-inoculating form may typify the odor and flavor descriptors of the green beer.