Fermentation

In order to accurately anticipate the proficiency of downdraft biomass gasification linked with a water–gas shift unit to produce biohydrogen, a model based on an artificial neural network (ANN) approach is established to estimate the specific mass flow rate of the biohydrogen output of the plant based on different types of biomasses and diverse operating parameters. The factors considered as inputs to the models are elemental and proximate analysis compositions as well as the operating parameters. The model structure includes one layer for input, a hidden layer and output layer. One thousand eight hundred samples derived from the simulation of 50 various feedstocks in different operating situations were utilized to train the developed ANN model. The established ANN in the case of product biohydrogen presents satisfactory agreement with input data: absolute fraction of variance (R²) is more than 0.999 and root mean square error (RMSE) is lower than 0.25. In addition, the relative impact of biomass properties and operating parameters on output are studied. At the end, to have a comprehensive evaluation, variations of the inputs regarding hydrogen-content are compared and evaluated together. The results show that almost all of the inputs show a significant impact on the sm_hydrogen output. Significantly, gasifier temperature, SBR, moisture content and hydrogen have the highest impacts on the sm_hydrogen with contributions of 19.96, 17.18, 15.3 and 10.48%, respectively. In addition, other variables in feed properties, like C, O, S and N present a range of 1.28–8.6% and proximate components like VM, FC and A present a range of 3.14–7.67% of impact on sm_hydrogen. Full article

Rice husk (RH) is one of the most important crop residues around the world, making its valorization an urgent and important topic in recent years. This work focused on the production of RH-based biochars at different pyrolysis temperatures from 400 to 900 °C and holding times from 0 to 90 min. Furthermore, the variations in the yields and pore properties of the resulting biochars were related to these process conditions. The results showed that the pore properties (i.e., BET surface area and porosity) of the resulting RH-based biochar were positively correlated with the ranges of pyrolysis temperature and holding time studied. The maximal pore properties with a BET surface area of around 280 m²/g and porosity of 0.316 can be obtained from the conditions at 900 °C for a holding time of 90 min. According to the data on the nitrogen (N₂) adsorption–desorption isotherms and pore size distributions, both microporous and mesoporous structures exist in the resulting biochar. In addition, the EDS and FTIR analyses also supported the slight hydrophilicity on the surface of the RH-based biochar due to the oxygen/silica-containing functional groups. Based on the findings of this work, the RH-based biochar could be used as a material in environmental applications for water conservation, wastewater treatment and soil amendment. Full article

Lactic acid bacteria (LAB) perform the process of malolactic fermentation (MLF) in wine. Availability of oxygen and nitrogen nutrients could influence LAB growth, malolactic activity, and other metabolic pathways, impacting the subsequent wine quality. The impact of these two factors has received limited investigation within LAB, especially on a transcriptome level. The aim of this study was to evaluate metabolic changes in the strain Lactiplantibacillus plantarum IWBT B063, growing in synthetic grape juice medium (GJM) under different oxygen exposure conditions, and with low availability of nitrogen-based nutrients. Next-generation sequencing was used to analyze expression across the transcriptome (RNA-seq), in combination with conventional microbiological and chemical analysis. L. plantarum consumed the malic acid present in all the conditions evaluated, with a slight delay and impaired growth for nitrogen limitation and for anaerobiosis. Comparison of L. plantarum transcriptome during growth in GJM with and without O₂ revealed differential expression of 148 functionally annotated genes, which were mostly involved in carbohydrate metabolism, genetic information processing, and signaling and cellular processes. In particular, genes with a protective role against oxidative stress and genes related to amino acid metabolism were differentially expressed. This study confirms the suitability of L. plantarum IWBT B063 to carry out MLF in different environmental conditions due to its potential adaption to the stress conditions tested and provides a better understanding of the genetic background of an industrially relevant strain. Full article

This study evaluated the microbial quality, safety, and ecology of a retail delicatessen Galotyri-like fresh acid-curd cheese traditionally produced by mixing fresh natural Greek yogurt with ‘Myzithrenio’, a naturally fermented and ripened whey cheese variety. Five retail cheese batches (mean pH 4.1) were analyzed for total and selective microbial counts, and 150 presumptive isolates of lactic acid bacteria (LAB) were characterized biochemically. Additionally, the most and the least diversified batches were subjected to a culture-independent 16S rRNA gene sequencing analysis. LAB prevailed in all cheeses followed by yeasts. Enterobacteria, pseudomonads, and staphylococci were present as <100 viable cells/g of cheese. The yogurt starters Streptococcus thermophilus and Lactobacillus delbrueckii were the most abundant LAB isolates, followed by nonstarter strains of Lactiplantibacillus, Lacticaseibacillus, Enterococcus faecium, E. faecalis, and Leuconostoc mesenteroides, whose isolation frequency was batch-dependent. Lactococcus lactis isolates were sporadic, except for one cheese batch. However, Lactococcus lactis, Enterobacteriaceae, Vibrionaceae, Salinivibrio, and Shewanellaceae were detected at fairly high relative abundances culture-independently, despite the fact that their viable counts in the cheeses were low or undetectable. Metagenomics confirmed the prevalence of S. thermophilus and Lb. delbrueckii. Overall, this delicatessen Galotyri-like cheese product was shown to be a rich pool of indigenous nonstarter LAB strains, which deserve further biotechnological investigation. Full article

Previous research has shown that hops contain enzymes able to hydrolyze unfermentable dextrins into fermentable sugars when added during the dry-hopping process. In the presence of live yeast, these additional fermentable sugars can lead to an over-attenuation of the beer; a phenomenon known as “hop creep”. This study attempts to analyze the effect of different Saccharomyces yeast species and strains on hop creep, with the intent to find an ability to mitigate the effects of dry-hop creep by using a specific yeast. Thirty different yeast species and strains were chosen from commercial and academic collections and propagated for pilot fermentations. Brews were performed at the Anheuser-Busch Research Brewery (1.8 hL, 10 °P, 20 IBU) at UC Davis and split to 40 L cylindroconical fermenters, with one fermenter in each yeast pair receiving 10 g/L Centennial hop pellets towards the end of fermentation. Standard analytical measurements were performed over the course of fermentation, with real degrees of fermentation (RDF) and extract measured on an Anton Paar alcolyzer. In order to preemptively determine the amount of hop creep to be experienced with each unknown fermentation, bench-top fermentations with 20 g/L dry-hops were performed concurrently and compared to the pilot scale fermentations. RDF was significantly higher (p < 0.01) on dry-hopped than non-dry-hopped fermentations beginning two days post dry-hopping to the end of fermentation, with the exceptions of SafAle™ BE-134, a S. cerevisiae var. diastaticus, and UCDFST 11-510, a S. mikatae. No apparent correlation between flocculation and increased RDF was shown in dry-hopped treatments. pH was significantly different between the dry-hopped and non-hopped fermentations (p < 0.05 one day post dry-hop, p < 0.01 for all subsequent days); this may have impacted on additional attenuation. No yeasts in this study indicated their use for mitigation of dry-hop creep, but this is a first look at beer fermentation for some of the chosen yeasts. The results also present a new perspective on how hop creep varies in fermentation. Full article

The existence of antibiotic-resistant bacteria in food products, particularly those carrying acquired resistance genes, has increased concerns about the transmission of these genes from beneficial microbes to human pathogens. In this study, we evaluated the antibiotic resistance-susceptibility patterns of 16 antibiotics in eight S. thermophilus strains, whose genome sequence is available, using phenotypic and genomic approaches. The minimal inhibitory concentration values collected revealed intermediate resistance to aminoglycosides, whereas susceptibility was detected for different classes of β-lactams, quinolones, glycopeptide, macrolides, and sulfonamides in all strains. A high tetracycline resistance level has been detected in strain M17PTZA496, whose genome analysis indicated the presence of the tet(S) gene and the multidrug and toxic compound extrusion (MATE) family efflux pump. Moreover, an in-depth genomic analysis revealed genomic islands and an integrative and mobilizable element (IME) in the proximity of the gene tet(S). However, despite the presence of a prophage, genomic islands, and IME, no horizontal gene transfer was detected to Lactobacillus delbrueckii subsp. lactis DSM 20355 and Lactobacillusrhamnosus GG during 24 h of skim milk fermentation, 2 weeks of refrigerated storage, and 4 h of simulated gastrointestinal transit. Full article

Background: Cava is considered to be a high-quality wine internationally. Hence, it has undergone consistent improvement and/or the preservation of its aromatic qualities, bouquet, color, and foamability, throughout its elaboration and aging. Methods: This study investigates the use of different Saccharomyces and non-Saccharomyces yeasts strains (Torulaspora delbrueckii and Metschnikowia pulcherrima) in Chardonnay and Xarel.lo cava wines. The usual enological parameters, the volatile composition, the protein contents, and foamability were determined, and sensory analyses were also performed for all of the vinifications (both before tirage and after 18 months of aging on the lees). Results: the protein and foamability results show that there is a direct relationship between both parameters, with better foam persistence achieved in some non-Saccharomyces fermentation. M. pulcherrima base wines showed a high protein content, improving foamability and foaming persistence. In addition, the results of the aromatic composition and the sensory analysis showed that the use of T. delbrueckii at first fermentation produced interesting cavas from an aromatic perspective. These cavas showed the highest values of ethyl isovalerate (120–126 µg/L), providing aromatic fruity notes, especially fresh green apple. Conclusions: the use of non-Saccharomyces yeasts in the base wine fermentation can be an alternative to produce cavas with differentiated aromatic characteristics and interesting foaming ability. Full article

Plant-based foods are rich sources of vitamins and essential micronutrients. For the proper functioning of the human body and their crucial role, trace minerals (iron, zinc, magnesium, manganese, etc.) are required in appropriate amounts. Cereals and pulses are the chief sources of these trace minerals. Despite these minerals, adequate consumption of plant foods cannot fulfill the human body’s total nutrient requirement. Plant foods also contain ample amounts of anti-nutritional factors such as phytate, tannins, phenols, oxalates, etc. These factors can compromise the bioavailability of several essential micronutrients in plant foods. However, literature reports show that fermentation and related processing methods can improve nutrient and mineral bioavailability of plant foods. In this review, studies related to fermentation methods that can be used to improve micronutrient bioavailability in plant foods are discussed. Full article

The Kluyveromyces marxianus yeast recently has gained considerable attention due to its applicability in high-value-added product manufacturing. In order to intensify the biosynthesis rate of a target product, reaching high biomass concentrations in the reaction medium is mandatory. Fed-batch processes are an attractive and efficient way how to achieve high cell densities. However, depending on the physiology of the particular microbial strain, an optimal media composition should be used to avoid by-product synthesis and, subsequently, a decrease in overall process effi-ciency. Thus, the aim of the present study was to optimise the synthetic growth medium and feeding solution compositions (in terms of carbon, nitrogen, phosphorous, magnesium, and calcium concentrations) for high cell density K. marxianus fed‑batch cultivations. Additionally, the biomass yields from the vitamin mixture and other macro/microelements were identified. A model predictive control algorithm was successfully applied for a fed-batch cultivation control. Biomass growth and substrate consumption kinetics were compared with the mathematical model predictions. Finally, 2‑phenylethanol biosynthesis was induced and its productivity was estimated. The determined optimal macronutrient ratio for K. marxianus biomass growth was identified as C:N:P = 1:0.07:0.011. The maximal attained yeast biomass concentration was close to 70 g·L^-1 and the 2-PE biosynthesis rate was 0.372 g·L⁻¹·h⁻¹, with a yield of 74% from 2-phenylalanine. Full article

Wood and forestry residues are usually processed as wastes, but they can be recovered to produce electrical and thermal energy through processes of thermochemical conversion of gasification. This study proposes an equilibrium simulation model developed by ASPEN Plus to investigate the performance of 28 woody biomass and forestry residues’ (WB&FR) gasification in a downdraft gasifier linked with a power generation unit. The case study assesses power generation in Iceland from one ton of each feedstock. The results for the WB&FR alternatives show that the net power generated from one ton of input feedstock to the system is in intervals of 0 to 400 kW/ton, that more that 50% of the systems are located in the range of 100 to 200 kW/ton, and that, among them, the gasification system derived by tamarack bark significantly outranks all other systems by producing 363 kW/ton. Moreover, the environmental impact of these systems is assessed based on the impact categories of global warming (GWP), acidification (AP), and eutrophication (EP) potentials and normalizes the environmental impact. The results show that electricity generation from WB&FR gasification is environmentally friendly for 75% of the studied systems (confirmed by a normalized environmental impact [NEI] less than 10) and that the systems fed by tamarack bark and birch bark, with an NEI lower than 5, significantly outrank all other systems owing to the favorable results obtained in the environmental sector. Full article

From a ‘farm to fork’ perspective, there are several phases in the production chain of fruits and vegetables in which undesired microbial contaminations can attack foodstuff. In managing these diseases, harvest is a crucial point for shifting the intervention criteria. While in preharvest, pest management consists of tailored agricultural practices, in postharvest, the contaminations are treated using specific (bio)technological approaches (physical, chemical, biological). Some issues connect the ‘pre’ and ‘post’, aligning some problems and possible solution. The colonisation of undesired microorganisms in preharvest can affect the postharvest quality, influencing crop production, yield and storage. Postharvest practices can ‘amplify’ the contamination, favouring microbial spread and provoking injures of the product, which can sustain microbial growth. In this context, microbial biocontrol is a biological strategy receiving increasing interest as sustainable innovation. Microbial-based biotools can find application both to control plant diseases and to reduce contaminations on the product, and therefore, can be considered biocontrol solutions in preharvest or in postharvest. Numerous microbial antagonists (fungi, yeasts and bacteria) can be used in the field and during storage, as reported by laboratory and industrial-scale studies. This review aims to examine the main microbial-based tools potentially representing sustainable bioprotective biotechnologies, focusing on the biotools that overtake the boundaries between pre- and postharvest applications protecting quality against microbial decay. Full article

As barley and oat production have recently increased in Canada, it has become prudent to investigate these cereal crops as potential feedstocks for alcoholic fermentation. Ethanol and other coproduct yields can vary substantially among fermented feedstocks, which currently consist primarily of wheat and corn. In this study, the liquified mash of milled grains from 28 barley (hulled and hull-less) and 12 oat cultivars were fermented with Saccharomyces cerevisiae to determine concentrations of fermentation products (ethanol, isopropanol, acetic acid, lactic acid, succinic acid, α-glycerylphosphorylcholine (α-GPC), and glycerol). On average, the fermentation of barley produced significantly higher amounts of ethanol, isopropanol, acetic acid, succinic acid, α-GPC, and glycerol than that of oats. The best performing barley cultivars were able to produce up to 78.48 g/L (CDC Clear) ethanol and 1.81 g/L α-GPC (CDC Cowboy). Furthermore, the presence of milled hulls did not impact ethanol yield amongst barley cultivars. Due to its superior ethanol yield compared to oats, barley is a suitable feedstock for ethanol production. In addition, the accumulation of α-GPC could add considerable value to the fermentation of these cereal crops. Full article

Paraburkholderia sp. SOS3 is a plant growth-promoting bacterium (PGPB) that displays pleiotropic effects and has the potential to be applied at a large scale across several agronomically important crops. The use of SOS3 is a suitable option to reduce the use of chemical fertilisers. While the benefits of SOS3 have been demonstrated in vitro, its potential applications at large scale are limited due to low biomass yield in current batch culture systems. Here, we developed a strategy for high-cell density cultivation of SOS3 in instrumented bioreactors, moving from low-biomass yield in a complex medium to high-biomass yield in a semi-defined medium. We achieved a 40-fold increase in biomass production, achieving cell densities of up to 11 g/L (OD₆₀₀ = 40). This result was achieved when SOS3 was cultivated using a fed-batch strategy. Biomass productivity, initially 0.02 g/L/h in batch cultures, was improved 12-fold, reaching 0.24 g/L/h during fed-batch cultures. The biomass yield was also improved 10-fold from 0.07 to 0.71 g_biomass/g_solids. Analysis of the fermentation profile of SOS3 indicated minimal production of by-products and accumulation of polyhydroxybutyrate (PHB) during the exponential growth phase associated with nitrogen limitation in the medium. By implementing proteomics analysis in fed-batch cultures, we identified the expression of four metabolic pathways associated with growth-promoting effects, which may be used as a qualitative parameter to guarantee the efficacy of SOS3 when used as a bioinoculant. Ultimately, we confirmed that the high-cell density cultures maintained their plant growth-promoting capacity when tested in sorghum and maize under glasshouse conditions. Full article

Sulfite is widely used as a preservative in foods and beverages for its antimicrobial and antioxidant activities, particularly in winemaking where SO₂ is frequently added. Thus, sulfite resistance mechanisms have been extensively studied in the fermenting yeast Saccharomyces cerevisiae. Nevertheless, in recent years, a negative perception has developed towards sulfites in wine, because of human health and environmental concerns. Increasing consumer demand for wines with low SO₂ content is pushing the winemaking sector to develop new practices in order to reduce sulfite content in wine, including the use of physical and chemical alternatives to SO₂, and the exploitation of microbial resources to the same purpose. For this reason, the formation of sulfur-containing compounds by wine yeast has become a crucial point of research during the last decades. In this context, the aim of this review is to examine the main mechanisms weaponized by Saccharomyces cerevisiae for coping with sulfite, with a particular emphasis on the production of sulfite and glutathione, sulfite detoxification through membrane efflux (together with the genetic determinants thereof), and production of SO₂-binding compounds. Full article

Bacillus velezensis ST03 and ST32, Bacillus amyloliquefaciens ST06 and ST109, and Bacillus subtilis ST08 were isolated from artisanal-produced kimchi and were identified based on 16S rRNA partial sequencing. DNA obtained from the investigated bacilli generated positive results for lichenicidin, iturin, subtilosin, and surfactin on a strain-specific basis. The strains were found to produce antimicrobial metabolites with activity levels ranging between 800 and 1600 AU/mL on a strain-specific basis, as determined against Listeria monocytogenes ATCC15313. Moreover, all tested strains in this study were still active after treatment with proteolytic enzymes, even with reduced inhibition zones compared to the controls, pointing to additional antimicrobial activity possibly related to a non-proteinaceous molecular structure. Most probably these strains may express surfactin as an additional factor in their complex antimicrobial activity. B. amyloliquefaciens ST09 and B. velezensis ST03 and ST32 were characterized as positive for β-hemolysis. B. subtilis ST08 was shown to be positive for hblC and nheC and B. amyloliquefaciens ST109 for nheB. B. amyloliquefaciens ST109 generated positive results for gelatinase activity. The ability of the studied Bacillus strains to metabolize different carbohydrate sources was done based on the API50CHB test, while the enzyme production profile was recorded by the APIZym kit. All studied strains were positive producers for biogenic amines production. Studied Bacillus spp. strains were resistant to some of the evaluated antibiotics, tested according to recommendations of CLSI and EFSA. Full article

Although results of recent studies suggest that fermented foods strongly affect the gut microbiota composition and that they relieve inflammatory bowel disease symptoms, some reports have described that fermented foods increase some inflammation markers based on differences in fermented food materials. This study evaluated the effects of fermented plant extract (FPE) on dextran sulfate sodium (DSS)-induced colitis in mice and the effects on fecal microbiota composition in humans. Mice fed 5% FPE with 3% DSS (FPE group) showed no body weight loss, atrophy of colonic length, or bloody stool, similar to mice fed a basal diet (negative group), whereas mice fed 3% DSS (positive group) exhibited those effects. Concentrations of inflammation markers IL-6 and TNF-α were not significantly different between FPE and negative groups; however, those concentrations became higher in the positive group. 16S ribosomal RNA gene sequencing was used to characterize fecal microbiota in healthy women before and after 3-month FPE supplementation. The FPE supplementation induced increases in Firmicutes phyla and in Clostridiales order, which play a central role in inflammation suppression. These results suggest that FPE enhances Clostridiales growth in the gut and that it has an anti-inflammatory effect. Full article

One of the main targets of sustainable development is the reduction of environmental, social, and economic negative externalities associated with the production of foods and beverages. Those externalities occur at different stages of food chains, from the farm to the fork, with deleterious impacts to different extents. Increasing evidence testifies to the potential of microbial-based solutions and fermentative processes as mitigating strategies to reduce negative externalities in food systems. In several cases, innovative solutions might find in situ applications from the farm to the fork, including advances in food matrices by means of tailored fermentative processes. This viewpoint recalls the attention on microbial biotechnologies as a field of bioeconomy and of ‘green’ innovations to improve sustainability and resilience of agri-food systems alleviating environmental, economic, and social undesired externalities. We argue that food scientists could systematically consider the potential of microbes as ‘mitigating agents’ in all research and development activities dealing with fermentation and microbial-based biotechnologies in the agri-food sector. This aims to conciliate process and product innovations with a development respectful of future generations’ needs and with the aptitude of the systems to overcome global challenges. Full article

Coffee pulp, mucilage, and beans with mucilage were used to develop alcoholic beverages. The pulp of 45.3% pulp, 54.7% mucilage with seed, and 9.4% mucilage only were obtained during the wet processing of coffee. Musts were prepared for all to TSS (Total soluble solid) 18 °Bx and fermentation was carried out for 12–16 days until TSS decreased to 5 °Bx at 30 °C. Phenolic characteristics, chromatic structures, chemical parameters, and sensory characteristics were analyzed for the prepared alcoholic beverages. Methanol content, ester content, aldehyde, alcohol, total acidity, caffeine, polyphenols, flavonoids, chromatic structure, and hue of the alcoholic beverage from the pulp was 335 mg/L, 70.58 ppm, 9.15 ppm, 8.86 ABV%, 0.41%, 30.94 ppm, 845.7 mg GAE/g dry extract, 440.7 mg QE/g dry extract, 0.41, and 1.71, respectively. An alcoholic beverage from the pulp was found superior to an alcoholic beverage from mucilage with beans and a beverage from mucilage in sensory analysis. There is the possibility of developing fermented alcoholic beverages from coffee pulp and mucilage. However, further research is necessary for quality of the beans that were obtained from the fermentation with the mucilage. Full article