Annotated whole-genome sequences of fermentative and spoilage associated Bacilli and proteobacteria autochthonous to commercial cucumber fermentation.

We report 36 whole-genome sequences, along with annotations, of fermentative (n = 12) and spoilage associated (n = 6) lactic acid bacteria, Lysinibacillus (n = 3), Streptococcus (n = 1), and Proteobacteria (n = 14) isolated from commercial cucumber fermentations. Fifty-three percent of the genome sequence assemblies consist of 1-4 contigs, and the remainder have fewer than 16.

CO2-mediated bloater defect can be induced by the uncontrolled growth of Enterobacteriaceae in cucumber fermentation.

Enterobacteriaceae are known to proliferate in cucumber juice, deriving energy from the fermentation of sugars to organic acids and ethanol, and theoretically generating carbon dioxide (CO2). We hypothesized that the CO2 produced by the indigenous Enterobacteriaceae in the early stage of cucumber fermentation accumulates in the fermenting fruits causing bloater defect. The ability of seven Enterobacteriaceae, indigenous to cucumber, to grow and produce CO2 in cucumber juice medium (CJM), a sterile model system for cucumber fermentation, was characterized. The induction of bloater defect in cucumber fermentation conducted with pasteurized and acidified fruits was also evaluated. The generation times of the seven Enterobacteriaceae in CJM ranged between 0.25 and 8.20 h and resulted in carbon dioxide (CO2) production to estimated amounts of 7.22-171.5 mM. Enterobacter cancerogenus and Enterobacter nimipressuralis were among the bacteria that produced the most and the least CO2 in CJM, respectively, at estimated mM concentrations of 171.58 ± 42.96 and 16.85 ± 6.53. Inoculation of E. cancerogenus and E. nimipressuralis in acidified and pasteurized cucumbers resulted in the production of 138 and 27 mM CO2, respectively. Such Enterobacteriaceae produced 2% hydrogen in the model cucumber fermentations. A bloater index of 25.4 and 17.4 was calculated from the cucumbers fermented by E. cancerogenus and E. nimipressuralis, respectively, whereas no defect was observed in the fruits collected from uninoculated control fermentation jars. It is concluded that the metabolic activity of the Enterobacteriaceae indigenous to cucumber can produce sufficient CO2 in cucumber fermentations to induce bloater defect.

Levilactobacillus brevis, autochthonous to cucumber fermentation, is unable to utilize citric acid and encodes for a putative 1,2-propanediol utilization microcompartment.

The metabolic versatility of Levilactobacillus brevis, a heterofermentative lactic acid bacterium, could benefit environmentally compatible and low salt cucumber fermentation. The biodiversity of Lvb. brevis autochthonous to cucumber fermentation was studied using genotypic and phenotypic analyses to identify unique adjunct cultures. A group of 131 isolates autochthonous to industrial fermentations was screened using rep-PCR-(GTG)5 and a fermentation ability assay under varied combinations of salt (0 or 6%), initial pH (4.0 or 5.2), and temperature (15 or 30°C). No apparent similarities were observed among the seven and nine clusters in the genotypic and phenotypic dendrograms, respectively. A total of 14 isolates representing the observed biodiversity were subjected to comparative genome analysis. The autochthonous Lvb. brevis clustered apart from allochthonous isolates, as their genomes lack templates for citrate lyase, several putative hypothetical proteins, and some plasmid- and phage-associated proteins. Four and two representative autochthonous and allochthonous Lvb. brevis, respectively, were subjected to phenotype microarray analysis using an Omnilog. Growth of all Lvb. brevis strains was supported to various levels by glucose, fructose, gentiobiose, 1,2-propanediol, and propionic acid, whereas the allochthonous isolate ATCC14890 was unique in utilizing citric acid. All the Lvb. brevis genomes encode for 1,2-propanediol utilization microcompartments. This study identified a unique Lvb. brevis strain, autochthonous to cucumber, as a potential functional adjunct culture for commercial fermentation that is distinct in metabolic activities from allochthonous isolates of the same species.

Genome-Wide Comparative Analysis of Lactiplantibacillus pentosus Isolates Autochthonous to Cucumber Fermentation Reveals Subclades of Divergent Ancestry.

Lactiplantibacillus pentosus, commonly isolated from commercial cucumber fermentation, is a promising candidate for starter culture formulation due to its ability to achieve complete sugar utilization to an end pH of 3.3. In this study, we conducted a comparative genomic analysis encompassing 24 L. pentosus and 3 Lactiplantibacillus plantarum isolates autochthonous to commercial cucumber fermentation and 47 lactobacillales reference genomes to determine species specificity and provide insights into niche adaptation. Results showed that metrics such as average nucleotide identity score, emulated Rep-PCR-(GTG)5, computed multi-locus sequence typing (MLST), and multiple open reading frame (ORF)-based phylogenetic trees can robustly and consistently distinguish the two closely related species. Phylogenetic trees based on the alignment of 587 common ORFs separated the L. pentosus autochthonous cucumber isolates from olive fermentation isolates into clade A and B, respectively. The L. pentosus autochthonous clade partitions into subclades A.I, A.II, and A.III, suggesting substantial intraspecies diversity in the cucumber fermentation habitat. The hypervariable sequences within CRISPR arrays revealed recent evolutionary history, which aligns with the L. pentosus subclades identified in the phylogenetic trees constructed. While L. plantarum autochthonous to cucumber fermentation only encode for Type II-A CRISPR arrays, autochthonous L. pentosus clade B codes for Type I-E and L. pentosus clade A hosts both types of arrays. L. pentosus 7.8.2, for which phylogeny could not be defined using the varied methods employed, was found to uniquely encode for four distinct Type I-E CRISPR arrays and a Type II-A array. Prophage sequences in varied isolates evidence the presence of adaptive immunity in the candidate starter cultures isolated from vegetable fermentation as observed in dairy counterparts. This study provides insight into the genomic features of industrial Lactiplantibacillus species, the level of species differentiation in a vegetable fermentation habitat, and diversity profile of relevance in the selection of functional starter cultures.

Whole-genome sequencing and annotation of selected Enterobacteriaceae derived from commercial cucumber fermentation.

We report five whole-genome sequences, along with annotations, representing Enterobacteriaceae from the genera Enterobacter (n = 1), Pantoea (n = 1), and Leclercia (n = 3) isolated from commercial cucumber fermentations performed in North Carolina and Minnesota, USA.

Whole-Genome Sequencing and Annotation of Pediococcus ethanolidurans and Pediococcus pentosaceus Isolates from Commercial Cucumber Fermentation.

We report the whole-genome sequences, along with annotations, of five Pediococcus ethanolidurans and three Pediococcus pentosaceus isolates from commercial cucumber fermentations performed in North Carolina (n = 3) and Minnesota (n = 5), USA.

Prevention of microbes-induced spoilage in sodium chloride-free cucumber fermentations employing preservatives.

This study evaluated preservatives to stabilize sodium chloride (NaCl)-free-cucumber fermentations. The brining of air-purged laboratory cucumber fermentations with 100.0 mM calcium chloride (CaCl2 ) and 25.0 mM acetic acid resulted in immediate rises in pH, the chemical reduction of the medium, and malodors. Supplementation with 3.0 mM sodium benzoate or 3.0 mM potassium sorbate enabled a decline in pH, a continuous oxidative state of the medium, and delayed rising pH spoilage. However, lactic and acetic acids eventually disappeared in fermentations supplemented with preservatives. The amount of preservatives needed to suppress growth of brined-cucumber-spoilage microbes was determined in Fermented Cucumber Juice Medium (FCJM). Supplementation of FCJM with 10.0 mM sodium benzoate was inhibitory for the spoilage yeasts, Issatchenkia occidentalis and Pichia manshurica, and the lactobacilli, Lentilactobacillus buchneri and Lentilactobacillus parafarraginis, but not of Zygosaccharomyces globiformis. Potassium sorbate inhibited the spoilage yeasts at 15.0 mM in FCJM but not the lactobacilli. Supplementation of FCJM with 20.0 mM fumaric acid had a bactericidal effect on the spoilage-associated lactobacilli. As expected, NaCl-free-commercial cucumber fermentations brined with 100 mM CaCl2 , no acetic acid, and 6 mM potassium sorbate resulted in complete fermentations, but supported rising pH, microbially induced spoilage during long-term storage. Post-fermentation supplementation with 12 mM sodium benzoate, 10 mM fumaric acid, a combination of the two, or 10 mM fumaric acid and 2 mM AITC prevented microbial activity during long-term bulk storage. PRACTICAL APPLICATION: Several preservative-based strategies for stabilizing NaCl-free cucumber fermentation in a commercial production setting were developed, enabling the implementation of a processing technology that reduces wastewater volumes and environmental impact.

Growth of ɣ-Proteobacteria in Low Salt Cucumber Fermentation Is Prevented by Lactobacilli and the Cover Brine Ingredients.

This study investigated the ability of É£-proteobacteria, indigenous to fresh cucumber, to grow in the expressed fruit juice (CJM) and fermentation. It was hypothesized that fresh cucumbers can support prolific growth of É£-proteobacteria but that the cover brine composition and acid production by the competing lactobacilli in the fermentation of the fruit act as inhibitory agents. The É£-proteobacteria proliferated in CJM with an average maximum growth rate (µmax) of 0.3895 ± 0.0929 and doubling time (Td) of 1.885 ± 0.465/h. A significant difference was found between the É£-proteobacteria µmax and Td relative to Lactiplantibacillus pentosus LA0445 (0.2319 ± 0.019; 2.89/h) and Levilactobacillus brevis 7.2.43 (0.221 ± 0.015; 3.35/h) but not Lactiplantibacillus plantarum 3.2.8 (0.412 ± 0.119; 1.87/h). While inoculation level insignificantly altered the µmax and Td of the bacteria tested; it impacted the length of lag and stationary phases for the lactobacilli. Unlike the lactobacilli, the É£-proteobacteria were inhibited in CJM supplemented with a low salt fermentation cover brine containing calcium chloride, acetic acid and potassium sorbate. The É£-proteobacteria, P. agglomerans, was unable to proliferate in cucumber fermentations brined with calcium chloride at a pH of 6.0 ± 0.1 and the population of Enterobacteriaceae was outcompeted by the lactobacilli within 36 h. Together these observations demonstrate that the prolific growth of É£-proteobacteria in CJM is not replicated in cucumber fermentation. While the É£-proteobacteria growth rate is faster that most lactobacilli in CJM, their growth in cucumber fermentation is prevented by the cover brine and the acid produced by the indigenous lactobacilli. Thus, the lactobacilli indigenous to cucumber and cover brine composition influence the safety and quality of fermented cucumbers. IMPORTANCE While the abundance of specific É£-proteobacteria species varies among vegetable type, several harbor Enterobacteriaceae and Pseudomonadaceae that benefit the plant system. It is documented that such bacterial populations decrease in density early in vegetable fermentations. Consequently, it is assumed that they do not contribute to the quality of finished products. This study explored the viability of É£-proteobacteria in CJM, used as a model system, CJM supplemented with fermentation cover brine and cucumber fermentation, which are characterized by an extremely acidic endpoint pH (3.23 ± 0.17; n = 391). The data presented demonstrates that fresh cucumbers provide the nutrients needed by É£-proteobacteria to proliferate and reduce pH to 4.47 ± 0.12. However, É£-proteobacteria are unable to proliferate in cucumber fermentation. Control of É£-proteobacteria in fermentations depends on the cover brine constituents and the indigenous competing lactobacilli. This knowledge is of importance when developing guidelines for the safe fermentation of vegetables, particularly with low salt.

Genome Sequences for Levilactobacillus brevis Autochthonous to Commercial Cucumber Fermentations.

We report the whole-genome sequences, along with annotations, of 11 Levilactobacillus brevis isolates from commercial cucumber fermentations performed in North Carolina (n = 9) and Minnesota (n = 2), USA.

Vegetable fermentations brined with low salt for reclaiming food waste.

Fermentation of eight vegetables was studied as an alternative for reclamation of surplus volumes. Fermentation performance was predicted by comparing the amounts of acid that could be produced from the intrinsic sugar content with that buffered by the fresh vegetable matrices prior to reaching an inhibitory pH for fermentative microbes (3.30). Native fermentations were brined with 345.0 mM sodium chloride, 40.0 mM calcium chloride, 6.0 mM potassium sorbate, and vinegar to adjust the initial pH to 4.70. High-performance liquid chromatography analysis, pH, and carbon dioxide measurements and spiral plating on selective media were employed to monitor the progress of fermentations. The average colony counts for yeast and/or molds and Enterobacteriaceae declined to undetectable levels from 3.6 ± 1.5 log CFU/ml within 7 days of fermentation. The fermentation of sugars produced lactic, acetic, succinic, and/or malic acids, and ethanol. As predicted, the fermentation of vegetables with low sugar content, such as broccoli, green leaf lettuce, and green pea proceeded to completion. The fermentation of vegetables with a moderate sugar content, such as green bell pepper, red ripened tomato, and green bean were incomplete at pH 3.1 ± 0.2. The fermentation of high sugar vegetables including sweet potato and corn were expected and observed to be incomplete. It is concluded that the intrinsic sugar content and buffer capacity of surplus vegetables are relevant parameters in obtaining complete fermentations. PRACTICAL APPLICATION: Vegetables are the second most wasted commodity in the United States and a substantial constituent of the global food waste. Development of fermentation to reclaim surplus vegetables from farms, grocery stores, and farmer's markets offers opportunities to ameliorate economic losses and environmental impact and add value to waste. The research described here suggests that a fraction of vegetables could be fermented in cover brines while others, with high sugar content, need specialized handling. Evidently, optimization of vegetable fermentation with starter cultures and added buffers represent an opportunity to stimulate complete bioconversions useful for reclaiming surplus volumes.

Whole-Genome Sequencing and Annotation of Selected Lactobacillales Isolated from Commercial Cucumber Fermentation.

We report the whole-genome sequences and annotations of 42 Lactobacillales isolated from commercial cucumber fermentations performed in North Carolina (n = 34) and Minnesota (n = 9), USA. The isolates include representatives from 12 acid-producing species.

Identification of potential causative agents of the CO2-mediated bloater defect in low salt cucumber fermentation.

Development of bloater defect in cucumber fermentations is the result of carbon dioxide (CO2) production by the indigenous microbiota. The amounts of CO2 needed to cause bloater defect in cucumber fermentations brined with low salt and potential microbial contributors of the gas were identified. The carbonation of acidified cucumbers showed that 28.68 ± 6.04 mM (12%) or higher dissolved CO2 induces bloater defect. The microbiome and biochemistry of cucumber fermentations (n = 9) brined with 25 mM calcium chloride (CaCl2) and 345 mM sodium chloride (NaCl) or 1.06 M NaCl were monitored on day 0, 2, 3, 5, 8, 15 and 21 using culture dependent and independent microbiological techniques and High-Performance Liquid Chromatography. Changes in pH, CO2 concentrations and the incidence of bloater defect were also followed. The enumeration of Enterobacteriaceae on Violet Red Bile Glucose agar plates detected a cell density of 5.2 ± 0.7 log CFU/g on day 2, which declined to undetectable levels by day 8. A metagenomic analysis identified Leuconostocaceae in all fermentations at 10 to 62%. The presence of both bacterial families in fermentations brined with CaCl2 and NaCl coincided with a bloater index of 24.0 ± 10.3 to 58.8 ± 23.9. The prevalence of Lactobacillaceae in a cucumber fermentation brined with NaCl with a bloater index of 41.7 on day 5 suggests a contribution to bloater defect. This study identifies the utilization of sugars and malic acid by the cucumber indigenous Lactobacillaceae, Leuconostocaceae and Enterobacteriaceae as potential contributors to CO2 production during cucumber fermentation and the consequent bloater defect.

Genotypic and phenotypic diversity among Lactobacillus plantarum and Lactobacillus pentosus isolated from industrial scale cucumber fermentations.

The Lactobacillus plantarum and Lactobacillus pentosus genotypes existing in industrial-scale cucumber fermentations were defined using rep-PCR-(GTG)5. The ability of each genotype to ferment cucumbers under various conditions was evaluated. Rep-PCR-(GTG)5 was the technique capable of illustrating the most intraspecies discrimination compared to the sequencing of housekeeping genes (recA, dnaK, pheS and rpoA), MLST and RAPD with primers LP1, OPL5, M14 and COC. Ten genotypic clusters were defined for the 199 L. pentosus tested and three for the 17 L. plantarum clones. The ability of the 216 clones genotyped and 37 additional cucumber fermentation isolates, of the same species, to rapidly decrease the pH of cucumber juice medium under various combinations of sodium chloride (0 or 6%), initial pH (4.0 or 5.2) and temperatures (15 or 30 °C) was determined using a fractional factorial screening design. A reduced fermentation ability was observed for the L. plantarum strains as compared to L. pentosus, except for clone 3.2.8, which had a ropy phenotype and aligned to genotypic cluster A. L. pentosus strains belonging to three genotypic clusters (B, D and J) were more efficient in cucumber juice fermentation as compared to most L. plantarum strains. This research identified three genetically diverse L. pentosus strains and one L. plantarum as candidates for starter cultures for commercial cucumber fermentations.

Gentiobiose and cellobiose content in fresh and fermenting cucumbers and utilization of such disaccharides by lactic acid bacteria in fermented cucumber juice medium.

The content of cellobiose and gentiobiose, cellulose-derived dissacharides, in fresh and fermented cucumber was evaluated along with the ability of Lactobacillus plantarum, Lactobacillus pentosus, Lactobacillus buchneri and Lactobacillus brevis to utilize them during and after fermentation. The disaccharide content in fresh and fermenting cucumbers was below the detection level (10 µM) using HPLC for analysis. Utilization of cellobiose and gentiobiose by lactic acid bacteria (LAB) was tested in fermented cucumber juice medium (FCJM), a model system for the bioconversion and postfermentation lacking glucose and fructose. Changes in the fermentation metabolites were followed using HPLC and pH measurements as a function of time. The disaccharides were utilized by L. plantarum, L. pentosus, and L. buchneri in FCJM at pH 4.7 ± 0.1, representative of the active fermentation period, and converted to lactic acid. The disaccharides were not utilized in FCJM at pH 3.7 ± 0.1, representative of the end of fermentation. While L. brevis was unable to utilize cellobiose efficiently in FCJM, they were able to remove gentiobiose at pH 4.7 ± 0.1. Some strain level differences in cellobiose utilization were observed. It is concluded that the disaccharides are absent in the fresh cucumber and the typical fermentation. The LAB prevalent in the bioconversion utilizes cellobiose and gentiobiose, if available, at pH 4.7 ± 0.1. The LAB would not remove the disaccharides, which could become available from cellulose degradation by the acid resistant indigenous microbiota, after the pH is reduced to 3.7 ± 0.1.

Characterization of robust Lactobacillus plantarum and Lactobacillus pentosus starter cultures for environmentally friendly low-salt cucumber fermentations.

Seven candidates for starter cultures for cucumber fermentations belonging to the Lactobacillus pentosus and Lactobacillus plantarum species were characterized based on physiological features desired for pickling. The isolates presented variable carbohydrate utilization profile on API® 50CHL test strips. The L. pentosus strains were unable to utilize d-xylose in MRS broth or the M medium. The lactobacilli were unable to produce histamine, tyramine, putrescine, and cadaverine in biogenic amine broth containing the necessary precursors. Production of d-lactic acid by the lactobacilli, detected enzymatically, was stimulated by growth in MRS broth as compared to cucumber juice medium (CJM). The lactobacilli utilized malic acid in the malate decarboxylase medium. Exopolyssacharide biosynthesis related genes were amplified from the lactobacilli. A sugar type-dependent-ropy phenotype was apparent for all the cultures tested in MRS and CJM. The genes associated with bacteriocin production were detected in the lactobacilli, but not the respective phenotypes. The antibiotic susceptibility profile of the lactobacilli mimics that of other L. plantarum starter cultures. It is concluded that the lactobacilli strains studied here are suitable starter cultures for cucumber fermentation. PRACTICAL APPLICATION: The availability of such starter cultures enables the implementation of low salt cucumber fermentations that can generate products with consistent biochemistry and microbiological profile.

Bacteriophages Infecting Gram-Negative Bacteria in a Commercial Cucumber Fermentation.

Cucumber fermentations are one of the most important vegetable fermentations in the United States. The fermentation is usually driven by lactic acid bacteria (LAB) indigenous to fresh cucumbers. But LAB are greatly outnumbered by many Gram-negative bacteria on fresh cucumbers, which may influence the growth of LAB and the incidence of bloater defect (hollow cavities formed inside fermented cucumbers) leading to serious economic loss to the pickle industry. Rapid elimination of Gram-negative bacteria is crucial to the dominance of LAB and the reduction of bloater defect in the fermentation. Various factors can affect the viability of Gram-negative bacteria in cucumber fermentation. Bacteriophages (phages) may be one of such factors. This study explored the abundance, diversity, and functional role of phages infecting Gram-negative bacteria in a commercial cucumber fermentation. Cover brine samples were taken from a commercial fermentation tank over a 30-day period. On day 1 and day 3 of the fermentation, 39 Gram-negative bacteria and 26 independent phages were isolated. Nearly 67% of Gram-negative bacterial isolates were susceptible to phage infection. Phage hosts include Enterobacter, Citrobacter, Escherichia, Pantoea, Serratia, Leclercia, Providencia, and Pseudomonas species. About 88% of the isolated phages infected the members in the family Enterobacteriaceae and 58% of phages infected Enterobacter species. Eight phages with unique host ranges were characterized. These phages belong to the Myoviridae, Siphoviridae, or Podoviridae family and showed distinct protein profiles and DNA fingerprints. The infectivity of a phage against Enterobacter cancerogenus was evaluated in cucumber juice as a model system. The phage infection at the multiplicity of infection 1 or 100 resulted in a 5-log reduction in cell concentration within 3 h and rapidly eliminated its host. This study revealed the abundance and variety of phages infecting Gram-negative bacteria, particularly Enterobacteriaceae, in the commercial cucumber fermentation, suggesting that phages may play an important role in the elimination of Gram-negative bacteria, thereby facilitating the dominance of LAB and minimizing bloater defect. To our knowledge, this is the first report on the ecology of phages infecting Gram-negative bacteria in commercial cucumber fermentations.

Content of xylose, trehalose and l-citrulline in cucumber fermentations and utilization of such compounds by certain lactic acid bacteria.

This research determined the concentration of trehalose, xylose and l-citrulline in fresh and fermented cucumbers and their utilization by Lactobacillus pentosus, Lactobacillus plantarum, Lactobacillus brevis and Lactobacillus buchneri. Targeted compounds were measured by HPLC and the ability of the lactobacilli to utilize them was scrutinized in fermented cucumber juice. Fresh cucumber juice was supplemented with trehalose, xylose and l-citrulline to observed mixed culture fermentations. Changes in the biochemistry, pH and colony counts during fermentations were monitored. Trehalose, xylose and l-citrulline were detected in fermentations to15.51 ± 1.68 mM, a fresh cucumber sample at 36.05 mM and in fresh and fermented cucumber samples at 1.05 ± 0.63 mM, respectively. Most of the LAB tested utilized trehalose and xylose in FCJM at pH 4.7. l-citrulline was utilized by L. buchneri and produced by other LAB. l-citrulline (12.43 ± 2.3 mM) was converted to ammonia (14.54 ± 3.60 mM) and the biogenic amine ornithine (14.19 ± 1.07 mM) by L. buchneri at pH 4.7 in the presence of 0.5 ± 0.2 mM glucose enhancing growth by 0.5 log CFU/mL. The use of a mixed starter culture containing L. buchneri aided in the removal of l-citrulline and enhanced the fermentation stability. The utilization of l-citrulline by L. buchneri may be a cause of concern for the stability of cucumber fermentations at pH 3.7 or above. This study identifies the use of a tripartite starter culture as an enhancer of microbial stability for fermented cucumbers.

Contribution of Leuconostocaceae to CO2-mediated bloater defect in cucumber fermentation.

Fermented cucumber bloater defect, caused by the accumulation of microbiologically produced carbon dioxide (CO2), creates significant economic losses for the pickling industry. The ability of Leuconostocaceae, indigenous to cucumber, to grow and produce CO2 during a fermentation and cause bloater defect was evaluated. Leuconostocaceae grew and produced over 40% CO2 in cucumber juice medium, used as a model for cucumber fermentation. The inoculation of Leuconostocaceae to 5 Log CFU/g in cucumber fermentations brined with 25 mM calcium chloride and 6 mM potassium sorbate resulted in no significant differences in bloater defect, colony counts from MRS and VRBG agar plates or the fermentation biochemistry; suggesting an inability of the inoculated bacterial species to prevail in the bioconversion. Acidified cucumbers were subjected to a fermentation inoculated with a Leuconostoc lactis starter culture after raising the pH to 5.9 ± 0.4. CO2 was produced in the acidified cucumber fermentations to 13.6 ± 3.5% yielding a bloater index of 21.3 ± 6.4; while 8.6 ± 0.8% CO2 and a bloater index of 5.2 ± 5.9 were observed in the non-inoculated control jars. Together the data collected demonstrate that Leuconostocaceae can produce enough CO2 to contribute to bloater defect, if not outcompeted by the leading lactic acid bacteria in a cucumber fermentation.

Isolation of Exopolysaccharide-Producing Yeast and Lactic Acid Bacteria from Quinoa (Chenopodium Quinoa) Sourdough Fermentation.

Quinoa, a nutritional grain, can be used as an ingredient in gluten-free sourdoughs. This study characterizes quinoa flour spontaneous fermentation with emphasis in the isolation of exopolysaccharide (EPS) producer bacteria. Real, red and black grains were studied. Dough yield, microbiota composition and fermentation biochemistry were determined for a total of 36 quinoa flour fermentations. The fermentation biochemistry was monitored by high-performance liquid chromatography (HPLC) analysis, pH measurement and titratable acidity. Changes in the microbiota were monitored by plating on deMann Rogosa and Sharp 5 agar (MRS5) and yeast and mold agar (YMA) plates and with metagenetic analysis. The ability to produce exopolysaccharides was screened in selected lactic acid bacteria (LAB) isolates. Production of organic acids in the spontaneous fermentation dropped the pH to 4.0 ± 0.3. The community of presumptive LAB reached 8.37 ± 0.01 log colony forming units (CFU)/mL by day 8 of back-slopped fermentations. The microbiota was composed of Lactobacillus, Enterococcus, Leuconostoc, Lactococcus, Pediococcus and Weissella. P. pentosaceous, L. citreum and W. cibaria were able to produce EPS in a starch-rich medium. P. pentosaceous showed higher exopolysaccharide yield, rapid acidifying kinetics and was able to drop the dough broth pH to values below 4.0 and a positive fermentation quotient after 24 h of incubation. Therefore, the bacterium might be a potential candidate for quinoa sourdough production.