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Fermentation, Volume 5, Issue 1 (March 2019)

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Open AccessArticle Direct Ethanol Production from Lignocellulosic Materials by Mixed Culture of Wood Rot Fungi Schizophyllum commune, Bjerkandera adusta, and Fomitopsis palustris
Fermentation 2019, 5(1), 21; https://doi.org/10.3390/fermentation5010021 (registering DOI)
Received: 31 January 2019 / Revised: 9 February 2019 / Accepted: 13 February 2019 / Published: 15 February 2019
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Abstract
The cost of bioethanol production from lignocellulosic materials is relatively high because the additional processes of delignification and saccharification are required. Consolidated bioprocessing (CBP) simultaneously uses the multiple processes of delignification, saccharification, and fermentation in a single reactor and has the potential to [...] Read more.
The cost of bioethanol production from lignocellulosic materials is relatively high because the additional processes of delignification and saccharification are required. Consolidated bioprocessing (CBP) simultaneously uses the multiple processes of delignification, saccharification, and fermentation in a single reactor and has the potential to solve the problem of cost. Some wood-degrading basidiomycetes have lignin- and cellulose-degrading abilities as well as ethanol fermentation ability. The white rot fungus Schizophyllum commune NBRC 4928 was selected as a strong fermenter from a previous study. The lignin-degrading fungus Bjerkandera adusta and polysaccharide-degrading fungus Fomitopsis palustris were respectively added to S. commune ethanol fermentations to help degrade lignocellulosic materials. Bjerkandera adusta produced more ligninase under aerobic conditions, so a switching aeration condition was adopted. The mixed culture of S. commune and B. adusta promoted direct ethanol production from cedar wood. Fomitopsis palustris produced enzymes that released glucose from both carboxymethylcellulose and microcrystalline cellulose. The mixed culture of S. commune and F. palustris did not enhance ethanol production from cedar. The combination of S. commune and cellulase significantly increased the rate of ethanol production. The results suggest that CBP for ethanol production from cellulosic material can be achieved by using multiple fungi in one reactor. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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Open AccessCommunication Influence of Media Heat Sterilization Process on Growth Performance of Representative Strains of the Genus Lactobacillus
Fermentation 2019, 5(1), 20; https://doi.org/10.3390/fermentation5010020
Received: 27 December 2018 / Revised: 5 February 2019 / Accepted: 11 February 2019 / Published: 15 February 2019
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Abstract
Lactic acid bacteria (LAB) are widely applied microorganisms in food, feed, and beverage applications, where they can provide essential functionality for product modification, increase product shelf life, or act as beneficial organisms after consumption. Among these, strains of the genus Lactobacillus are often [...] Read more.
Lactic acid bacteria (LAB) are widely applied microorganisms in food, feed, and beverage applications, where they can provide essential functionality for product modification, increase product shelf life, or act as beneficial organisms after consumption. Among these, strains of the genus Lactobacillus are often used as starters, probiotics, or biopreservatives. For all these types of bacterial preparations, a transportable shelf-stable form of concentrated bacteria, preserving their intrinsic properties, is essential for commercial distribution. Former studies revealed a relationship between the culture medium, cellular morphology, and the robustness of Lactobacillus acidophilus NCFM (name derived from North Carolina Food Microbiology) cultures. Due to these insights, a multitude of Lactobacillus strains representative of the genus were screened regarding their sensitivity to thermal medium pretreatment possibly accompanied by the alteration of their chemical composition, such as the formation of Maillard reaction products (MRPs). This study reveals a quite diverse and different growth behavior of those strains in the form of altered or non-altered cell concentrations and the size distributions of the populations, whereby five strains of the L. delbrueckii group in particular showed increased cell concentrations combined with decreased mean cell volumes. The results are of both scientific and industrial relevance, as they highlight the necessity to consider and understand the effects of media sterilization for the applied production strain. Full article
(This article belongs to the Special Issue Lactic Acid Fermentation and the Colours of Biotechnology)
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Open AccessEditorial Wine Fermentation
Fermentation 2019, 5(1), 19; https://doi.org/10.3390/fermentation5010019
Received: 2 February 2019 / Accepted: 9 February 2019 / Published: 12 February 2019
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Abstract
Currently wineries are facing new challenges due to actual market demands for creation of products exhibiting more individual flavors[...] Full article
(This article belongs to the Special Issue Wine Fermentation)
Open AccessArticle Application of a Multienzymatic System from Natural Latex in Key Reactions for oil-Based Biorefineries
Fermentation 2019, 5(1), 18; https://doi.org/10.3390/fermentation5010018
Received: 29 December 2018 / Revised: 23 January 2019 / Accepted: 29 January 2019 / Published: 2 February 2019
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Abstract
Oil-based biorefineries play a crucial role in the production of key platform chemicals that can be generated via biotechnological processes instead of a petrochemical route. This work focuses on the latex of the fruit of Araujia sericifera, which can be considered a [...] Read more.
Oil-based biorefineries play a crucial role in the production of key platform chemicals that can be generated via biotechnological processes instead of a petrochemical route. This work focuses on the latex of the fruit of Araujia sericifera, which can be considered a multienzymatic system with applications in key reactions in oil-based biorefineries. The latex of Araujia sericifera (ASL) was used as a novel biocatalyst in the esterification of oleic acid and in the hydrolysis of triglycerides and p-nitrophenyl carboxylates. When ASL was compared to a commercial biocatalyst, it showed an excellent activity in the hydrolysis of soybean oil and p-nitropheyl laurate, and a comparable activity in the esterification reaction. Full article
(This article belongs to the Special Issue Fermentation Process in Biorefinery)
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Open AccessArticle Kinetic Study on Heterotrophic Growth of Acetobacterium woodii on Lignocellulosic Substrates for Acetic Acid Production
Fermentation 2019, 5(1), 17; https://doi.org/10.3390/fermentation5010017
Received: 31 December 2018 / Revised: 28 January 2019 / Accepted: 29 January 2019 / Published: 2 February 2019
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Abstract
Extensive research has been done on examining the autotrophic growth of Acetobacterium woodii with gaseous substrates (hydrogen and carbon dioxide) to produce acetic acid. However, only limited work has been performed on the heterotrophic growth of A. woodii using pure sugars or lignocellulosic [...] Read more.
Extensive research has been done on examining the autotrophic growth of Acetobacterium woodii with gaseous substrates (hydrogen and carbon dioxide) to produce acetic acid. However, only limited work has been performed on the heterotrophic growth of A. woodii using pure sugars or lignocellulosic feedstocks-derived sugars as substrates. In this study, we examine the growth kinetics and acetic acid production of A. woodii on glucose and xylose. While good growth was observed with glucose as substrate, no significant growth was obtained on xylose. Kinetic studies were performed in batch culture using different concentrations of glucose, ranging from 5 g/L to 40 g/L. The highest acetate production of 6.919 g/L with a product yield of 0.76 g acetic acid/g glucose was observed with 10 g/L glucose as initial substrate concentration. When testing A. woodii on corn stover hydrolysate (CSH) and wheat straw hydrolysate (WSH) formed after pretreatment and enzymatic hydrolysis, we found that A. woodii showed acetic acid production of 7.64 g/L and a product yield of 0.70 g acetic acid/g of glucose on WSH, while the acetic acid production was 7.83 g/L with a product yield of 0.65 g acetic acid/g of glucose on CSH. These results clearly demonstrate that A. woodii performed similarly on pure substrates and hydrolysates, and that the processes were not inhibited by the heterogenous components present in the lignocellulosic feedstock hydrolysates. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Open AccessFeature PaperArticle Effects of Ultrasound on Fermentation of Glucose to Ethanol by Saccharomyces cerevisiae
Fermentation 2019, 5(1), 16; https://doi.org/10.3390/fermentation5010016
Received: 31 December 2018 / Revised: 24 January 2019 / Accepted: 27 January 2019 / Published: 29 January 2019
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Abstract
Previous studies have shown that pretreatment of corn slurries using ultrasound improves starch release and ethanol yield during biofuel production. However, studies on its effects on the mass transfer of substrates and products during fermentation have shown that it can have both beneficial [...] Read more.
Previous studies have shown that pretreatment of corn slurries using ultrasound improves starch release and ethanol yield during biofuel production. However, studies on its effects on the mass transfer of substrates and products during fermentation have shown that it can have both beneficial and inhibitory effects. In this study, the effects of ultrasound on mass transfer limitations during fermentation were examined. Calculation of the external and intraparticle observable moduli under a range of conditions indicate that no external or intraparticle mass transfer limitations should exist for the mass transfer of glucose, ethanol, or carbon dioxide. Fermentations of glucose to ethanol using Saccharomyces cerevisiae were conducted at different ultrasound intensities to examine its effects on glucose uptake, ethanol production, and yeast population and viability. Four treatments were compared: direct ultrasound at intensities of 23 and 32 W/L, indirect ultrasound (1.4 W/L), and no-ultrasound. Direct and indirect ultrasound had negative effects on yeast performance and viability, and reduced the rates of glucose uptake and ethanol production. These results indicate that ultrasound during fermentation, at the levels applied, is inhibitory and not expected to improve mass transfer limitations. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Open AccessArticle Microwave-Assisted Extraction Applied to Merlot Grapes with Contrasting Maturity Levels: Effects on Phenolic Chemistry and Wine Color
Fermentation 2019, 5(1), 15; https://doi.org/10.3390/fermentation5010015
Received: 4 January 2019 / Revised: 23 January 2019 / Accepted: 24 January 2019 / Published: 28 January 2019
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Abstract
Merlot grapes were harvested with three maturity levels (21.1, 23.1, and 25.1 Brix), and processed with or without the application of microwave-assisted extraction (MW). The detailed phenolic composition and color were followed during winemaking. The MW treatment did not affect the basic chemical [...] Read more.
Merlot grapes were harvested with three maturity levels (21.1, 23.1, and 25.1 Brix), and processed with or without the application of microwave-assisted extraction (MW). The detailed phenolic composition and color were followed during winemaking. The MW treatment did not affect the basic chemical composition of the wines. Upon crushing, MW caused a 211% improvement in anthocyanins in the wines of the first harvest and an 89% improvement in the wines of the third harvest. At bottling, MW favored the formation of pyranoanthocyanins and tannin-anthocyanin dimers. Tannin extraction was not affected by MW just after application of this process, but improvements of 30, 20, and 10% on MW-treated wines of the first, second, and third harvest, respectively, were recorded at pressing. The formation of polymeric pigments during aging generally increased along with harvest date and was only favored in MW-treated wines of the first and third harvest, with preferential formation of small polymeric pigments, in accordance with enhanced anthocyanin extraction in these wines. Initial improvements of wine color upon application of MW in the wines of the first, second, and third harvest were of 275, 300, and 175%, respectively. Although these differences subsided or disappeared for the wines of the second and third harvest during aging, the wines of the first harvest treated with MW retained 52% more color than Control wines at day 150 post-crushing. Results suggest the MW treatment was more efficient in extracting and retaining phenolics and color when applied to unripe fruit. Full article
(This article belongs to the Special Issue Wine Fermentation)
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Open AccessArticle Optimization of an Industrial Medium from Molasses for Bioethanol Production Using the Taguchi Statistical Experimental-Design Method
Fermentation 2019, 5(1), 14; https://doi.org/10.3390/fermentation5010014
Received: 30 December 2018 / Revised: 23 January 2019 / Accepted: 24 January 2019 / Published: 26 January 2019
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Abstract
The production of bioethanol as a clean liquid fuel in a cost-effective way is highly desired by global energetics. Sugar beet molasses is a renewable and cheap substrate for the production of biotechnological products. Therefore, the aim of the current study was the [...] Read more.
The production of bioethanol as a clean liquid fuel in a cost-effective way is highly desired by global energetics. Sugar beet molasses is a renewable and cheap substrate for the production of biotechnological products. Therefore, the aim of the current study was the optimization of an industrial medium from molasses for bioethanol production using the Taguchi statistical experimental-design method. First, the growth rate of yeast cells and the amount of ethanol produced by the Saccharomyces cerevisiae strain sahand 101 were investigated in aerobic and aerobic–anaerobic conditions. The yeast strain produced 8% (v/v) bioethanol in a medium containing molasses with 18% Brix in aerobic–anaerobic conditions. The main factors of the medium, including molasses, ammonium sulfate, urea, and pH, were optimized for the increase of bioethanol production by the Taguchi method. Bioethanol production reached 10% (v/v) after optimization of the medium in flask culture. The yeast strain produced 11% (v/v) bioethanol in the bioreactor culture containing the optimized medium, which is an acceptable amount of bioethanol produced from molasses at the industrial scale. The results showed that the Taguchi method is an effective method for the design of experiments aiming to optimize the medium for bioethanol production by reducing the number of experiments and time. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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Open AccessArticle Enhanced Production and Quantitative Evaluation of Nigericin from the Algerian Soil-Living Streptomyces youssoufiensis SF10 Strain
Fermentation 2019, 5(1), 13; https://doi.org/10.3390/fermentation5010013
Received: 18 December 2018 / Revised: 17 January 2019 / Accepted: 22 January 2019 / Published: 26 January 2019
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Abstract
Nigericin, one of the main ionophoric polyethers produced by various Streptomyces strains, presents relevant biological activities including antibacterial and recently studied antitumor properties. This work describes the influence of different culture conditions on the production of this metabolite by Streptomyces sp. SF10, isolated [...] Read more.
Nigericin, one of the main ionophoric polyethers produced by various Streptomyces strains, presents relevant biological activities including antibacterial and recently studied antitumor properties. This work describes the influence of different culture conditions on the production of this metabolite by Streptomyces sp. SF10, isolated from a semi-arid soil sample collected at Chélia Mountain, in Khenchela (Northeastern Algeria) and identified as Streptomyces youssoufiensis. The extracts from the strain, cultured in a solid state or submerged fermentation conditions, using several carbon sources at different pH values, in the presence or absence of iron (II) sulfate and in co-culture with other Streptomyces species, were analyzed using a high-performance liquid chromatography (HPLC) system equipped with an evaporative light scattering detector (ELSD). The best culture conditions provided a concentration of nigericin of 0.490 ± 0.001 mg/mL in the extract. The HPLC-ELSD method, optimized here for the quantitative detection of nigericin, can find wider applications in the analysis of several other metabolites characterized by a similar polycyclic polyether structure or, more generally, by the lack of significant chromophores in their molecular structure. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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Open AccessArticle Impact of Hydrolysis Methods on the Utilization of Agricultural Residues as Nutrient Source for D-lactic Acid Production by Sporolactobacillus inulinus
Fermentation 2019, 5(1), 12; https://doi.org/10.3390/fermentation5010012
Received: 14 December 2018 / Revised: 21 January 2019 / Accepted: 22 January 2019 / Published: 23 January 2019
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Abstract
d-lactic acid is a building block for heat resistant polylactic acid, a biobased polymer with a high potential. Nevertheless, an economically efficient industrial process for d-lactic acid production still needs to be implemented. Yeast extract is an expensive nutrient source, which [...] Read more.
d-lactic acid is a building block for heat resistant polylactic acid, a biobased polymer with a high potential. Nevertheless, an economically efficient industrial process for d-lactic acid production still needs to be implemented. Yeast extract is an expensive nutrient source, which is used to fulfill the complex nutritional requirements in lactic acid fermentations. The substitution of yeast extract by cheap alternative nutrient sources is a challenge in many fermentation processes. In this study, chemical and enzymatic hydrolysis techniques for protein rich agricultural residues and their effectiveness are compared, as well as their impact on the d-lactic acid production of Sporolactobacillus inulinus. An efficient substitution of yeast extract could be achieved by a variety of agricultural residues, hydrolysed with 3M H2SO4, demonstrating the much higher versatility and effectiveness of this method compared to enzymatic methods. In a fed-batch experiment with chemically hydrolyzed rapeseed meal and minimal supplementation, a lactic acid titer of 221 g L−1 and an overall productivity of 1.55 g (L h)−1 (96% yield) were obtained. Full article
(This article belongs to the Special Issue Lactic Acid Fermentation and the Colours of Biotechnology)
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Open AccessArticle Improved Raoultella planticola Strains for the Production of 2,3-Butanediol from Glycerol
Fermentation 2019, 5(1), 11; https://doi.org/10.3390/fermentation5010011
Received: 14 December 2018 / Revised: 14 January 2019 / Accepted: 16 January 2019 / Published: 18 January 2019
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Abstract
Raw glycerol is an industrial byproduct from biodiesel production and is one of the most promising substrates for 2,3-butanediol (2,3-BD) production; however, 2,3-BD is not yet produced by fermentation from glycerol on a commercial scale due to poor process economics. Class 1 microorganism [...] Read more.
Raw glycerol is an industrial byproduct from biodiesel production and is one of the most promising substrates for 2,3-butanediol (2,3-BD) production; however, 2,3-BD is not yet produced by fermentation from glycerol on a commercial scale due to poor process economics. Class 1 microorganism collections were screened and Raoultella planticola strain CECT 843 proved to be the best 2,3-BD producer, achieving (23.3 ± 1.4) g 2,3-BD per L and a yield of 36% (g 2,3-BD per g glycerol). To further increase product concentration and yield, R. planticola CEC T843 was subjected to random mutagenesis using ultra-violet (UV) light and ethyl methane sulfonate (EMS). Two mutant strains were found to produce at least 30% more 2,3-BD than the wild type: R. planticola IA1 [(30.8 ± 3.9) g 2,3-BD per L and 49% yield] and R. planticola IIIA3 [(30.5 ± 0.4) g 2,3-BD per L and 49% yield]. Full article
(This article belongs to the Special Issue Fermentation Process in Biorefinery)
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Open AccessArticle Kinetic Parameters of Saccharomyces cerevisiae Alcohols Production Using Nepenthes mirabilis Pod Digestive Fluids-Mixed Agro-Waste Hydrolysates
Fermentation 2019, 5(1), 10; https://doi.org/10.3390/fermentation5010010
Received: 28 December 2018 / Revised: 12 January 2019 / Accepted: 14 January 2019 / Published: 17 January 2019
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Abstract
In this study, microbial growth kinetics and modeling of alcohols production using Saccharomyces cerevisiae were evaluated using different hydrolysates in a single pot (batch) system. Mixed agro-waste hydrolysates from different pre-treatment methods, i.e., N. mirabilis/CP and HWP/DAP/CP, were used as the sole [...] Read more.
In this study, microbial growth kinetics and modeling of alcohols production using Saccharomyces cerevisiae were evaluated using different hydrolysates in a single pot (batch) system. Mixed agro-waste hydrolysates from different pre-treatment methods, i.e., N. mirabilis/CP and HWP/DAP/CP, were used as the sole nutrient source in the fermentations used to produce the alcohols of interest. The maximum Saccharomyces cerevisiae concentration of 1.47 CFU/mL (×1010) was observed with HWP/DAP/CP hydrolysates, with a relative difference of 21.1% when compared to the N. mirabilis/CP cultures; the product yield based on biomass generation was relatively (20.2%) higher for the N. mirabilis/CP cultures. For the total residual phenolic compounds (TRPCs) generation, a relative difference (24.6%) between N. mirabilis/CP and HWP/DAP/CP pre-treatment systems was observed, suggesting that N. mirabilis/CP generates lower inhibition by-products. This was further evidenced by the lowest substrate utilization rate (3.3 × 10−4 g/(L·h)) for the N. mirabilis/CP cultures while achieving relatively similar product formation rates to those observed for the HWP/DAP/CP. A better correlation (R2 = 0.94) was obtained when predicting substrate utilization for the N. mirabilis/CP cultures. Generally, the pre-treatment of mixed agro-waste using N. mirabilis/CP seemed appropriate for producing hydrolysates which Saccharomyces cerevisiae can effectively use for alcohol production in the biorefinery industry. Full article
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Open AccessArticle Use of Chicken Feather Peptone and Sugar Beet Molasses as Low Cost Substrates for Xanthan Production by Xanthomonas campestris MO-03
Received: 18 December 2018 / Revised: 8 January 2019 / Accepted: 10 January 2019 / Published: 14 January 2019
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Abstract
Xanthan gum is one of the polysaccharides most commonly used in a broad range of industries (food, cosmetics, pharmaceutical, etc.). Agro-industrial by-products are being explored as alternative low-cost nutrients to produce xanthan gum by Xanthomonas campestris. In this study, for the production [...] Read more.
Xanthan gum is one of the polysaccharides most commonly used in a broad range of industries (food, cosmetics, pharmaceutical, etc.). Agro-industrial by-products are being explored as alternative low-cost nutrients to produce xanthan gum by Xanthomonas campestris. In this study, for the production of xanthan gum, sugar beet molasses and chicken feather peptone (CFP) were used as carbon and nitrogen sources, respectively. X. campestris produced the highest level of xanthan gum (20.5 g/L) at 60 h of cultivation using sugar beet molasses (40 g/L total sugar) supplemented with CFP (4 g/L) at pH 7, 200 rpm, and 30 °C. The pyruvic acid content of the xanthan gums increased with increasing CFP concentration. Compared with commercial organic nitrogen sources (tryptone, bacto peptone, and yeast extract), the highest production of xanthan gum was obtained with CFP. Moreover, among the tested peptones, the highest pyruvic acid (3.2%, w/w) content was obtained from CFP. The usage of sugar beet molasses and CFP as substrates in industries would enable a cost-efficient commercial production. These results suggest that sugar beet molasses and CFP can be used as available low-cost substrates for xanthan gum production by X. campestris. Full article
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Open AccessReview Quality Ingredients and Safety Concerns for Traditional Fermented Foods and Beverages from Asia: A Review
Received: 22 November 2018 / Revised: 12 December 2018 / Accepted: 2 January 2019 / Published: 10 January 2019
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Abstract
Fermented foods and beverages serve as vehicles for beneficial microorganisms that play an important role in human health and remain the oldest prevalent means of food processing and preservation. Traditional fermented foods are popular in Asia for their nutritional balance and food security. [...] Read more.
Fermented foods and beverages serve as vehicles for beneficial microorganisms that play an important role in human health and remain the oldest prevalent means of food processing and preservation. Traditional fermented foods are popular in Asia for their nutritional balance and food security. Techniques for preserving cereals, vegetables, and meat products are well developed in many Asian countries. Due to their cultural and nutritional significance, many of these foods have been studied in detail and their quality and safety have also been improved. These fermented foods and beverages provide benefits through enhanced nutritional content, digestibility, microbial stability, and detoxification. They represent is thus one of the most affordable and suitable methods to maintain hygiene condition and food quality and security in poor and underdeveloped countries. There is an industrial interest and scope related to traditional fermented foods and beverages in Asia. However, urgent attention is required to improve the quality of the ingredients and the integration of food safety management systems for industrial growth. Full article
(This article belongs to the Special Issue Safety and Microbiological Quality)
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Open AccessEditorial Acknowledgement to Reviewers of Fermentation in 2018
Published: 8 January 2019
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Abstract
Rigorous peer-review is the corner-stone of high-quality academic publishing. [...] Full article
Open AccessArticle Effects of Seawater on Carotenoid Production and Lipid Content of Engineered Saccharomyces cerevisiae
Received: 8 October 2018 / Revised: 13 December 2018 / Accepted: 24 December 2018 / Published: 1 January 2019
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Abstract
The use of seawater in fermentation can potentially reduce the freshwater burden in the bio-based production of chemicals and fuels. We previously developed a Saccharomyces cerevisiae carotenoids hyperproducer SM14 capable of accumulating 18 mg g−1 DCW (DCW: dry cell weight) of β-carotene [...] Read more.
The use of seawater in fermentation can potentially reduce the freshwater burden in the bio-based production of chemicals and fuels. We previously developed a Saccharomyces cerevisiae carotenoids hyperproducer SM14 capable of accumulating 18 mg g−1 DCW (DCW: dry cell weight) of β-carotene in rich media (YPD). In this work, the impacts of seawater on the carotenoid production of SM14 were investigated. When using nutrient-reduced media (0.1× YNB) in freshwater the β-carotene production of SM14 was 6.51 ± 0.37 mg g−1 DCW; however in synthetic seawater, the production was increased to 8.67 ± 0.62 mg g−1 DCW. We found that this improvement was partially due to the NaCl present in the synthetic seawater, since supplementation of 0.5 M NaCl in freshwater increased β-carotene production to 11.85 ± 0.77 mg g−1 DCW. The combination of synthetic seawater with higher carbon-to-nitrogen ratio (C:N = 50) further improved the β-carotene production to 10.44 ± 0.35 mg g−1 DCW. We further showed that the carotenoid production improvement in these conditions is related with lipid content and composition. These results demonstrated the benefit of using seawater to improve the production of carotenoids in S. cerevisiae, and have the potential to expand the utilization of seawater. Full article
(This article belongs to the Special Issue Postgenomic Microbial Physiology and Fermentation)
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Open AccessArticle Effect of Various Pretreatment Methods on Bioethanol Production from Cotton Stalks
Received: 3 December 2018 / Revised: 12 December 2018 / Accepted: 20 December 2018 / Published: 1 January 2019
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Abstract
Cotton stalks (CS) are considered a good candidate for fuel-ethanol production due to its abundance and high carbohydrate content, but the direct conversion without pretreatment always results in extremely low yields due to the recalcitrant nature of lignocelluloses. The present study was undertaken [...] Read more.
Cotton stalks (CS) are considered a good candidate for fuel-ethanol production due to its abundance and high carbohydrate content, but the direct conversion without pretreatment always results in extremely low yields due to the recalcitrant nature of lignocelluloses. The present study was undertaken to investigate the effect of various chemical and physicochemical pretreatment methods, i.e., alkali, microwave-assisted acid, organosolv, hydrothermal treatment, and sequentially organosolv and hydrothermal pretreatment, on chemical composition of CS and subsequent ethanol production applying pre-hydrolysis and simultaneous saccharification and fermentation (PSSF) at high solid loading. The best results in terms of ethanol production were achieved by the sequential combination of organosolv and hydrothermal pretreatment (32.3 g/L, using 15% w/v substrate concentration and 6 h pre-hydrolysis) with an improvement of 32% to 50% in ethanol production compared to the other pretreatments. Extending pre-hydrolysis time to 14 h and increasing substrate concentration to 20% w/v, ethanol production reached 47.0 g/L (corresponding to an ethanol yield of 52%) after 30 h of fermentation. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Open AccessReview Second Generation Bioethanol Production: On the Use of Pulp and Paper Industry Wastes as Feedstock
Received: 30 October 2018 / Revised: 1 December 2018 / Accepted: 19 December 2018 / Published: 24 December 2018
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Abstract
Due to the health and environment impacts of fossil fuels utilization, biofuels have been investigated as a potential alternative renewable source of energy. Bioethanol is currently the most produced biofuel, mainly of first generation, resulting in food-fuel competition. Second generation bioethanol is produced [...] Read more.
Due to the health and environment impacts of fossil fuels utilization, biofuels have been investigated as a potential alternative renewable source of energy. Bioethanol is currently the most produced biofuel, mainly of first generation, resulting in food-fuel competition. Second generation bioethanol is produced from lignocellulosic biomass, but a costly and difficult pretreatment is required. The pulp and paper industry has the biggest income of biomass for non-food-chain production, and, simultaneously generates a high amount of residues. According to the circular economy model, these residues, rich in monosaccharides, or even in polysaccharides besides lignin, can be utilized as a proper feedstock for second generation bioethanol production. Biorefineries can be integrated in the existing pulp and paper industrial plants by exploiting the high level of technology and also the infrastructures and logistics that are required to fractionate and handle woody biomass. This would contribute to the diversification of products and the increase of profitability of pulp and paper industry with additional environmental benefits. This work reviews the literature supporting the feasibility of producing ethanol from Kraft pulp, spent sulfite liquor, and pulp and paper sludge, presenting and discussing the practical attempt of biorefineries implementation in pulp and paper mills for bioethanol production. Full article
(This article belongs to the Special Issue Microbial Production of Added-value Products from Renewable Resources)
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Open AccessReview Nutritional and Microbiological Quality of Tiger Nut Tubers (Cyperus esculentus), Derived Plant-Based and Lactic Fermented Beverages
Received: 12 November 2018 / Revised: 17 December 2018 / Accepted: 19 December 2018 / Published: 20 December 2018
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Abstract
Tiger nut (Cyperus esculentus) is a tuber that can be consumed raw or processed into beverages. Its nutritional composition shows a high content of lipid and dietary fiber, close to those of nuts, and a high content of starch, like in [...] Read more.
Tiger nut (Cyperus esculentus) is a tuber that can be consumed raw or processed into beverages. Its nutritional composition shows a high content of lipid and dietary fiber, close to those of nuts, and a high content of starch, like in other tubers. Tiger nuts also contain high levels of phosphorus, calcium, and phenolic compounds, which contribute to their antioxidant activity. From those characteristics, tiger nuts and derived beverages are particularly relevant to limit food insecurity in regions where the plant can grow. In Europe and United States, the tiger nut derived beverages are of high interest as alternatives to milk and for gluten-free diets. Fermentation or addition of probiotic cultures to tiger nut beverages has proven the ability of lactic acid bacteria to acidify the beverages. Preliminary sensory assays concluded that acceptable products are obtained. In the absence of pasteurization, the safety of tiger nut-based beverages is not warranted. In spite of fermentation, some foodborne pathogens or mycotoxigenic fungi have been observed in fermented beverages. Further studies are required to select a tailored bacterial cocktail which would effectively dominate endogenous flora, preserve bioactive compounds and result in a well-accepted beverage. Full article
(This article belongs to the Special Issue Safety and Microbiological Quality)
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Open AccessArticle The Effect of Salt and Temperature on the Growth of Fresco Culture
Received: 26 October 2018 / Revised: 11 December 2018 / Accepted: 17 December 2018 / Published: 20 December 2018
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Abstract
The effect of environmental factors, including temperature and water activity, has a considerable impact on the growth dynamics of each microbial species, and it is complicated in the case of mixed cultures. Therefore, the aim of this study was to describe and analyze [...] Read more.
The effect of environmental factors, including temperature and water activity, has a considerable impact on the growth dynamics of each microbial species, and it is complicated in the case of mixed cultures. Therefore, the aim of this study was to describe and analyze the growth dynamics of Fresco culture (consisting of 3 different bacterial species) using predictive microbiology tools. The growth parameters from primary fitting were modelled against temperature using two different secondary models. The intensity of Fresco culture growth in milk was significantly affected by incubation temperature described by Gibson’s model, from which the optimal temperature for growth of 38.6 °C in milk was calculated. This cardinal temperature was verified with the Topt = 38.3 °C calculated by the CTMI model (cardinal temperature model with inflection), providing other cardinal temperatures, i.e., minimal Tmin = 4.0 °C and maximal Tmax = 49.6 °C for Fresco culture growth. The specific growth rate of the culture under optimal temperature was 1.56 h−1. The addition of 1% w/v salt stimulated the culture growth dynamics under temperatures down to 33 °C but not the rate of milk acidification. The prediction data were validated and can be used in dairy practice during manufacture of fermented dairy products. Full article
(This article belongs to the Special Issue Safety and Microbiological Quality)
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Open AccessArticle Changes in the Composition of the Lactic Acid Bacteria Behavior and the Diversity of Oenococcus oeni Isolated from Red Wines Supplemented with Selected Grape Phenolic Compounds
Received: 19 November 2018 / Revised: 17 December 2018 / Accepted: 18 December 2018 / Published: 20 December 2018
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Abstract
Phenolic compounds are important components of wine and are known to have an impact on the physiology of wine microbes. The influence of specific sub-sets of phenolic compounds on the growth and metabolism of lactic acid bacteria (LAB) and on the diversity of [...] Read more.
Phenolic compounds are important components of wine and are known to have an impact on the physiology of wine microbes. The influence of specific sub-sets of phenolic compounds on the growth and metabolism of lactic acid bacteria (LAB) and on the diversity of Oenococcus oeni in inoculated and non-inoculated red wines was investigated during malolactic fermentation (MLF) and subsequent storage. Representative O. oeni strains from wines treated with flavonols and trans-resveratrol were isolated and analyzed by pulsed-field gel electrophoresis of rare restriction enzyme digests (REA-PFGE). 28 days after MLF initiation, strains from all samples had entered the death phase, except those supplemented with trans-resveratrol. In the non-inoculated samples, the onset of lactic acid production was apparently delayed by all compounds tested, except for the flavan-3-ols. Increased levels of phenolics also delayed citrate consumption in inoculated samples. PFGE analysis revealed 22 genetic profiles, and some profiles were characteristics of specific samples. The commercial starter used in the inoculated wines did not dominate during MLF. The effect of the phenolics studied was dependent on the origin and concentration of each as well, as the fermentation stage and whether the wines were inoculated. The effect of flavonols and trans-resveratrol seemed to be strain-dependent, which could have implications on the final quality of wines. Full article
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Fermentation EISSN 2311-5637 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
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