Acid Fermentation Research Articles

The Novel Solution for Acid Whey Permeate Application in Animal Feeding

Abstract The experiment was conducted to analyse the effect of fermented acid whey permeate on milk yield and composition in the lactating cows. Propionic acid bacteria and their metabolites have been used in the lactating cows feeding over decades, primarily to improve growth performance, feed conversation and milk production efficiency. Two groups of the lactating cows were arranged in the study: control group (n=50) and experimental group (n=50). Experimental group’s animals received 0.5 L of fermented whey permeate daily. Acid whey permeate was inoculated with the freeze-dried PS-4 (Propionibacterium freudenreichii subsp. shermanii, Chr.Hansen, Denmark) starter and fermented anaerobically for 48 hours at 20±2 oC. Fat, protein, lactose and total solids concentration in acid whey permeate and fermented acid whey permeate was analysed by the standard methods, but propionic acid was detected by HPLC. Milk composition and quality indices were determined at the beginning of the study and each month during 6 months period. At the end of the study the feeding of fermented acid whey permeate was stopped, but milk composition and quality data were monitored additionally after one month. Milk fat, protein, lactose, total solids, urea concentration and somatic cell count were analysed by a near infrared spectroscopy. The variability in milk composition and quality data across trial was greater in the experiment group than in the control. Milk fat and somatic cell count were significantly different (p<0.05) than other studied parameters in the experimental group cows’ milk. Milk yield and lactose concentration were tended to increase during feeding of fermented acid whey permeate in the lactating cows without significant differences between control and experimental groups. Fermented acid whey permeate as feed supplement improves energy metabolism for dairy cows which results in the higher milk yield and fat concentration.

PSX-22 Nannochloropsis oculata microalgae as a natural source of rumen-protected eicosapentaenoic acid in diets of lactating Nubian goats

Abstract Dietary fats can affect lactational performance of goats and modify the profile of fatty acids in milk. The effects of providing lactating Nubian goats with Nannochloropsis oculata microalgae, as a natural source of rumen-protected eicosapentaenoic acid (EPA), on the feed intake, digestion, ruminal fermentation, lactational performance and milk fatty acid profile were evaluated. Fifteen lactating does, weighing 33.0 ± 1.3 kg after parturition, were randomly assigned to three treatments in a quintuplicated 3 × 3 Latin square design. Does were stratified according to their previous milk production, parity and expected average milk yield in a 12-week experiment. Does were fed a basal diet containing 300 g of berseem clover, 200 g wheat straw and 500 g of concentrates (control treatment) or the control diet supplemented with 5 g (NO5 treatment) or 10 g (NO10 treatment) of N. oculata microalgae. Dietary treatments did not affect feed intake but increased (P < 0.01) nutrient digestibility. Without affecting ruminal pH and ammonia-N, NO5 and NO10 treatments linearly increased total volatile fatty acids (P = 0.002) and propionic acid (P = 0.022). Dietary treatments linearly increased (P < 0.01) daily milk production and the concentration of lactose without affecting other milk components. Both NO5 and NO10 treatments decreased atherogenic index (P = 0.004) and increased the concentrations of unsaturated fatty acids and C20:5n3 (EPA). In conclusion, supplementing the diet of lactating Nubian goats with N. oculata microalgae at 5 and 10 g daily enhanced milk production and altered milk fatty acid composition. Although further research is needed, performance responses associated with increasing the dose of the microalgae from 5 g to 10 g /doe were not large; thus, the 5 g dose is recommended for practical use.

80 Effects of miscanthus fiber on nutrient digestibility and fecal metabolites of adult dogs

Abstract Dietary fiber is an important component of pet food that helps to promote colonocyte health by favoring saccharolytic fermentation and short-chain fatty acid production in addition to modulating gut microbiota and aiding laxation. The objective of this study was to evaluate and compare the effects of miscanthus grass fiber, prebiotic fiber blends, and traditional dietary fiber sources on apparent total tract digestibility, fecal metabolites, and gastrointestinal intolerance in adult canines. Animal procedures were approved by the University of Illinois Institutional Animal Care and Use Committee. Twelve female adult beagles were randomly assigned to one of six treatments containing cellulose, beet pulp, miscanthus fiber, or a blend of miscanthus fiber and tomato pomace, miscanthus fiber and resistant starch, or miscanthus fiber and fructooligosaccharide in a replicated 6x6 Latin square design. All treatment diets were formulated to meet or exceed AAFCO nutrient profile (2018). The dogs received each treatment for 21 d, with 17 d of diet adaptation followed by 4 d of total and fresh fecal collection. No difference in fecal score was observed (P < 0.05). Dogs fed the beet pulp diet had the highest organic matter digestibility and total dietary fiber digestibility (P < 0.05) when compared to all other treatments. Crude protein digestibility was significantly higher (P < 0.05) for the cellulose, miscanthus fiber, and miscanthus and resistant starch blend than the beet pulp diet. Fecal total short-chain fatty acid concentration was greatest for beet pulp and lowest for the cellulose treatment (P < 0.05) with the miscanthus fiber and miscanthus fiber blends with resistant starch, fructooligosaccharide, and tomato pomace being intermediate. No difference was observed in fecal total branched-chain fatty acid concentration (P < 0.05). The data suggest that miscanthus fiber is an adequate and functional source of fiber in extruded canine diets, and comparable to the traditional fiber source, cellulose.

Soaking induced discrepancies in oenological properties, flavor profiles, microbial community and sensory characteristic of Huangjiu (Chinese rice wine)

Soaking is a crucial process in adjusting initial fermentation acidity and achieving desired flavor quality of rice wines. Effects of soaking time on physicochemical characteristic of rice, flavor profiles, microbial community and sensory characteristic of Huangjiu were investigated. Soaking caused significantly changes in amylopectin content, and rice with high amylopectin content was conducive to produce esters and aldehydes during Hungjiu brewing. High-throughput sequencing showed that bacteria types were more abundant than fungi during brewing, suggesting that bacterial community might be primarily responsible for Huangjiu flavor. Differential analysis revealed that Weissella and Enterobacter contributed greatly to the accumulation of alcohols, esters and aldehydes during Huangjiu brewing, while Clostridium, Acinetobacter, Cyanobacteria, Zymomonas and Exiguobacterium were responsible for the rancidity. Based on spearman's correlation analysis, Lactococcus, Weissella, Pediococcus, Lactobacillus and Staphylococcus were the key microbial genera responsible for the flavor characteristic of Huangjiu. While favorable soaking caused an increased intensity in alcohol-aroma, full body and continuation of resultant Huangjiu, insufficient soaking led to a higher intensity of bitter taste. Summarily, soaking acidity ranged from 2 to 3 g/L was beneficial for preventing rancidity and improving the production of flavor compounds in Huangjiu.

Fine‐tuning ethanol oxidation pathway enzymes and cofactor PQQ coordinates the conflict between fitness and acetic acid production by Acetobacter pasteurianus

The very high concentrations required for industrial production of free acetic acid create toxicity and low pH values, which usually conflict with the host cell growth, leading to a poor productivity. Achieving a balance between cell fitness and product synthesis is the key challenge to improving acetic acid production efficiency in metabolic engineering. Here, we show that the synergistic regulation of alcohol/aldehyde dehydrogenase expression and cofactor PQQ level could not only efficiently relieve conflict between increased acetic acid production and compromised cell fitness, but also greatly enhance acetic acid tolerance of Acetobacter pasteurianus to a high initial concentration (3% v/v) of acetic acid. Combinatorial expression of adhA and pqqABCDE greatly shortens the duration of starting-up process from 116 to 99h, leading to a yield of 69gl-1 acetic acid in semi-continuous fermentation. As a final result, average acetic acid productivity has been raised to 0.99gl-1 h-1 , which was 32% higher than the parental A.pasteurianus. This study is of great significance for decreasing cost of semi-continuous fermentation for producing high-strength acetic acid industrially. We envisioned that this strategy will be useful for production of many other desired organic acids, especially those involving cofactor reactions.

Continuous in-situ extraction of acetic acid produced by Acetobacterium woodii during fermentation of hydrogen and carbon dioxide using Amberlite FPA53 ion exchange resins

Ion-exchange resins have emerged as a promising technology for separation of targeted products from biochemical production. In this study, in-situ acetic acid extraction using Amberlite FPA53 resins was examined. The study includes initial testing of the resins for separation of different concentrations of acetic acid in water along with continuous in-situ extraction of acetic acid from gas-liquid fermentation with Acetobacterium woodi on a mixture of 70% H2–30% CO2. An average acetic acid adsorption of 67.6 mg/g resin was achieved using Amberlite FPA53, significantly lower than the concentration obtained with pure acetic acid solutions (159.6 mg/g resin). This result indicates that pH and competing components in the fermentation broth influence the efficiency of the resin. Implementing in-situ extraction of acetic acid increased its production by 1.6-fold resulting in 10.21 g/L acetic acid for extractive fermentation compared to 6.4 g/L for the control, without continuous extraction of acetic acid.

Identification of nitric oxide (NO)-responsive genes under hypoxia in tomato (Solanum lycopersicum L.) root

Flooding periods, as one probable consequence of climate change, will lead more frequently to plant hypoxic stress. Hypoxia sensing and signaling in the root, as the first organ encountering low oxygen, is therefore crucial for plant survival under flooding. Nitric oxide has been shown to be one of the main players involved in hypoxia signaling through the regulation of ERFVII transcription factors stability. Using SNP as NO donor, we investigated the NO-responsive genes, which showed a significant response to hypoxia. We identified 395 genes being differentially regulated under both hypoxia and SNP-treatment. Among them, 251 genes showed up- or down-regulation under both conditions which were used for further biological analysis. Functional classification of these genes showed that they belong to different biological categories such as primary carbon and nitrogen metabolism (e.g. glycolysis, fermentation, protein and amino acid metabolism), nutrient and metabolites transport, redox homeostasis, hormone metabolism, regulation of transcription as well as response to biotic and abiotic stresses. Our data shed light on the NO-mediated gene expression modulation under hypoxia and provides potential targets playing a role in hypoxia tolerance. These genes are interesting candidates for further investigating their role in hypoxia signaling and survival.

Study on Dissolution Characteristics of Excess Sludge by Low-Temperature Thermal Hydrolysis and Acid Production by Fermentation.

To investigate the dissolution characteristics of low-temperature thermal pretreatment conditions and the process of sludge fermentation to produce acid, the influence of thermal pretreatment temperature on the dissolution of excess sludge organic composition and the mechanism of cell crushing of sludge thermal pretreatment were analyzed by an experimental method, and the performance of acid production was explored by sludge fermentation after pretreatment at different temperatures. The performance of acid production by sludge fermentation after pretreatment at different temperatures was measured. The results proved that the soluble chemical oxygen demand (SCOD) shows the largest increase in dissolution rate (11.92%) at 70 °C and in dissolution quantity (6518.33 mg/L) at 90 °C. However, at 80 °C, the solubility of total organic carbon (TOC) is the highest (3224.47 mg/L), and at 70 °C, the best dissolution conditions for soluble carbohydrate (SC) and soluble protein (SP) reached 340.07 and 80.92 mg/L, respectively. The degree of sludge breaking starts to increase at 70 °C. Correlation analysis shows that dissolved organic matter is mainly derived from the cell wall and intracellular material and SP is mainly derived from intracellular material. Excitation–emission matrix spectra and parallel factor analysis (EEM-PARAFAC) divides the sludge dissolved organic matter (DOM) into five fluorescent components, including C1 (318/366) tyrosine, C2 (418/470) UVA humic acid, C3 (282/334) tryptophan substances, C4 (322/430) UVC humic acids, and C5 (314, 382, 454/526) UVA humic substances. Fermentation acid production experiment shows that the peak concentration is highest at 80 °C, the arrival time is 2 days, and the acid production type is butyric acid fermentation. Thus, it is proved that low-temperature thermal pretreatment promotes the process of acid-producing fermentation and has no effect on the type of fermentation. The optimal condition for hydrolytic dissolution and acid production under low-temperature thermal pretreatment is 80 °C.

Microbial community in Chinese traditional fermented acid rice soup (rice-acid) and its correlations with key organic acids and volatile compounds

Rice-acid is a unique Chinese traditional fermented acid rice soup and its microbial community plays an important role in the formation of flavour compounds. In the study, rice-acid products from high-temperature and low-temperature fermentation methods were selected to analyze the microbial community, organic acids, and volatile flavour compounds (VFCs). The main bacterial and fungal phyla in Chinese traditional fermented rice-acid were determined to be Firmicutes and Ascomycota, including 62 bacterial genera and 57 fungal genera. The dominant bacterial genera were Lactobacillus, Acetobacter, and Prevotella and the dominant fungal genera were Naumovia, Pichia, Candida, and Saccharomyces. Among organic acids in rice-acid, L-lactic acid had the highest concentration, followed by malic acid, acetic acid, citric acid, oxalic acid, and tartaric acid. Volatile flavour compounds had a high contribution to the flavour, including ethyl acetate, ethanol, acetic acid, propanoic acid, 1-octen-3-ol, 2-nonanol, 2-undecanol, propyl propionate, ethyl propanoate, propyl propionate, and 2,3-butanedione. The microorganisms which were closely correlated with key organic acids in rice-acid included Lactobacillus, Acetobacter, Pichia, Candida, Kluyveromyces and Meyerozyma. The microorganisms which were correlated with VFCs included Acetobacter, Prevotella, Kluyveromyces and Saccharomyces. In particular, Lactobacillus, Pichia, Malassezia, Clavispora, Rhizopus and Cystofilobasidium were significantly positively correlated with lactic acid in rice-acid. Kluyveromyces, Saccharomyces and Emericella were significantly positively correlated with ethanol and ethyl acetate. The study provides the basis for improving the quality of rice-acid.

The Combined Effect of Pressure and Temperature on Kefir Production-A Case Study of Food Fermentation in Unconventional Conditions.

Food fermentation under pressure has been studied in recent years as a way to produce foods with novel properties. The purpose of this work was to study kefir production under pressure (7–50 MPa) at different temperatures (17–32 °C), as a case study of unconventional food fermentation. The fermentation time to produce kefir was similar at all temperatures (17, 25, and 32 °C) up to 15 MPa, compared to atmospheric pressure. At 50 MPa, the fermentation rate was slower, but the difference was reduced as temperature increased. During fermentation, lactic and acetic acid concentration increased while citric acid decreased. The positive activation volumes (Va) obtained indicate that pressure decreased the fermentation rate, while the temperature rise led to the attenuation of the pressure effect (lower Va). On the other hand, higher activation energies (Ea) were observed with pressure increase, indicating that fermentation became more sensitive to temperature. The condition that resulted in a faster fermentation, higher titratable acidity, and higher concentration of lactic acid was 15 MPa/32 °C. As the authors are aware, this is the second work in the literature to study the combined effect of pressure and temperature on a fermentative process.

Comparison of Different Lactobacilli Regarding Substrate Utilization and Their Tolerance Towards Lignocellulose Degradation Products

Fermentative lactic acid production is currently impeded by low pH tolerance of the production organisms, the successive substrate consumption of the strains and/or the requirement to apply purified substrate streams. We identified Lactobacillus brevis IGB 1.29 in compost, which is capable of producing lactic acid at low pH values from lignocellulose hydrolysates, simultaneously consuming glucose and xylose. In this study, we compared Lactobacillus brevis IGB 1.29 with the reference strains Lactobacillus brevis ATCC 367, Lactobacillus plantarum NCIMB 8826 and Lactococcus lactis JCM 7638 with regard to the consumption of C5- and C6-sugars. Simultaneous conversion of C5- and C6-monosaccharides was confirmed for L. brevis IGB 1.29 with consumption rates of 1.6 g/(L h) for glucose and 1.0 g/(L h) for xylose. Consumption rates were lower for L. brevis ATCC 367 with 0.6 g/(L h) for glucose and 0.2 g/(L h) for xylose. Further trials were carried out to determine the sensitivity towards common toxic degradation products in lignocellulose hydrolysates: acetate, hydroxymethylfurfural, furfural, formate, levulinic acid and phenolic compounds from hemicellulose fraction. L. lactis was the least tolerant strain towards the inhibitors, whereas L. brevis IGB 1.29 showed the highest tolerance. L. brevis IGB 1.29 exhibited only 10% growth reduction at concentrations of 26.0 g/L acetate, 1.2 g/L furfural, 5.0 g/L formate, 6.6 g/L hydroxymethylfurfural, 9.2 g/L levulinic acid or 2.2 g/L phenolic compounds. This study describes a new strain L. brevis IGB 1.29, that enables efficient lactic acid production with a lignocellulose-derived C5- and C6-sugar fraction.

Steady States of a Fermentation Process for Lactic Acid Production at a Given Concentration of the Main Substrate

A computational scheme has been presented that generalizes theoretical representations of a technology for the continuous fermentation of lactic acid at a given concentration of the main substrate in the stream that enters a fermenter. The sequence of constructing the computational scheme includes a preliminary analysis and a principal analysis. In the preliminary analysis, relationships have been derived that form the region of estimating the boundary characteristics that correspond to a given productivity of the process. The coordinates of the point of the maximum productivity $$\left[ {{{S}_{{{\text{opt}}}}},{\kern 1pt} {\kern 1pt} {\kern 1pt} {{D}^{{{\text{opt}}}}}} \right]$$ have been found. The coordinates of singular points have also been determined: $$\left[ {{{S}_{1}}\left( {{{D}_{1}}} \right),{{D}_{1}}} \right]$$ for singular point 1, $$\left[ {{{S}_{2}}\left( {{{D}_{2}}} \right),{{D}_{2}}} \right]$$ for singular point 2, $$\left[ {{{S}_{3}}\left( {{{D}_{3}}} \right),{{D}_{3}}} \right]$$ for singular point 3, and $$\left[ {{{S}_{4}}\left( {{{D}_{4}}} \right),{{D}_{4}}} \right]$$ for singular point 4. For the point of the maximum productivity and singular points, relationships have been presented for calculating the initial concentrations of the main substrate S0 and the corresponding initial concentrations of the component that produces the substrate during fermentation M0. The values of coordinates have been constraints in constructing relationships for the principal analysis that determine sets for selecting the values of M0 and D at a given value of S0. The scheme of the construction of sets consists of three sections, namely, I, II, and III. The boundaries of these sections are determined by relationships (21), (22), and (23), respectively. The sequence of the construction of sets for each of the sections has been presented, and it has been shown that there is one set (Set1) for section I, there are two sets (Set1* and Set2*) for section II, and there are three sets (Set1**, Set2**, and Set3**) for section III. Tables have been given for calculating the elements of sets at a given value of S0. The theoretical relationships that have been derived are used for numerical calculation to estimate the characteristics of the multiplicity of steady states for each of the sets. It is shown that the range of the assignment of S0 is the widest for section I, whereas the range of values for the dilution rate D is the greatest for section III. Numerical estimates in a comparative variant for sets in sections II and III have shown that the final concentrations of components under the same initial conditions differ in the values of M0, M, and S. This makes it possible to obtain comparative estimates for the further processing of produced components (the recovery of lactic acid, the recycling and use of unconverted components, the recovery of a by-product, and so on).

Bifidobacterium adolescentis shows potential to strengthen host defence against gastrointestinal infection via inhibition of the opportunistic pathogen Candida albicans and stimulation of human-isolated macrophages killing capacity in vitro

The human gut microbiota enhances the host’s resistance to enteric pathogens via colonisation resistance, a phenomenon that is driven by multiple mechanisms, such as production of antimicrobial metabolites and activation of host immune responses. However, there is limited information on how individual gut bacterial species, particularly many of the dominant anaerobes, might impact the host’s defence. This study investigated the potential of specific human gut isolates to bolster the host’s resistance to infection. First, by antagonising the opportunistic fungal pathogen Candida albicans, and secondly, by modulating the killing capacity of human-isolated macrophages in vitro. Co-culturing C. albicans with faecal microbiota from different healthy individuals revealed varying levels of fungal inhibition. In vitro assays with a panel of representative human gut anaerobes confirmed that culture supernatants from certain bacterial isolates, in particular of Bifidobacterium adolescentis, significantly inhibited C. albicans growth. Mechanistic studies revealed that microbial fermentation acids including acetate and lactate, in combination with the associated decrease in pH, were strong drivers of this inhibitory activity. In the second in vitro assay, human-isolated macrophages were exposed to bacterial supernatants, and subsequently tested for their capacity to eliminate adherent-invasive Escherichia coli. Among the gut anaerobes tested, B. adolescentis was revealed to exert the strongest immunostimulatory and killing effect when compared to the unstimulated macrophages control. B. adolescentis is known to be stimulated by dietary consumption of resistant starch andmay therefore represent an attractive target for the development of probiotic and prebiotic interventions tailored to enhancethe host’s natural defences against infection.

Effects of Methane Fermentation on Spectral Properties of Fulvic Acid Extracted from Peat through Liquid Acid Precipitation

The effects of acid precipitation with different liquid acids on spectral properties of fulvic acid extracted from peat was studied to select the most appropriate liquid acid for the acid precipitation step of the alkali solution acid precipitation method, and the new process mechanism of peat utilization by coupling methane fermentation and extraction of fulvic acid was analyzed. The alkali solution acid precipitation method was adopted to extract fulvic acid from the methane-fermented group and methane-unfermented group. Different liquid acids were used to conduct acid precipitation during the extraction. And then, the characterizations of fulvic acid samples were conducted through Fourier infrared spectroscopy, UV-Vis spectroscopy, and fluorescence spectroscopy. The yield and content of fulvic acid decreased significantly after methane fermentation. During the methane fermentation process, some fulvic acid was consumed and utilized by microorganisms to promote the methane fermentation process, resulting both in the decrease of methyl, hydroxyl, and ether bonds and in the increase of methylene, carbonyl, conjugated double bond, benzene rings, and other groups. The E4/E6 ratio shows that the E4/E6 ratio of fulvic acid was decreased after methane fermentation, and the fermentation consumed the functional group with simpler structure such as aliphatic chain hydrocarbon of fulvic acid while the structure with a higher degree of aromatization and conjugate cannot be consumed. When conducting acid precipitation with different liquid acids, the yield of fulvic acid was the highest through acid precipitation with phosphoric acid. The fulvic acid obtained through acid precipitation with nitric acid has a higher content, more benzene rings, and the highest degree of aromatization.

Reflux symptoms and oesophageal acidification in treated achalasia patients are often not reflux related

ObjectiveAfter treatment, achalasia patients often develop reflux symptoms. Aim of this case–control study was to investigate mechanisms underlying reflux symptoms in treated achalasia patients by analysing oesophageal function, acidification patterns...

Improved Production of Malic Acid in Aspergillus niger by Abolishing Citric Acid Accumulation and Enhancing Glycolytic Flux.

Microbial fermentation was widely explored to produce malic acid. Previously, Aspergillus niger has been successfully engineered, and a high titer of malic acid was achieved with strain S575, but it also produced a high level of byproduct citric acid. Here, the capability of A. niger in malic acid biosynthesis was further improved by eliminating the accumulation of citric acid and enhancing glycolytic flux. Characterization of variant mutants suggested that disruption of cexA, a gene encoding citric acid transporter located on cell membrane, abolished citric acid accumulation. However, cexA-deficient strain S895 showed significantly decreased malic acid production. Further analysis of S895 indicated that the transcription level of genes involved in glucose transportation and glycolytic pathway was significantly reduced, and the corresponding enzyme activity was also lower than those of S575. Individual overexpression of genes encoding glucose transporter MstC and key enzymes (hexokinase HxkA, 6-phosphofructo-2-kinase PfkA, and pyruvate kinase PkiA) involved in irreversible reactions of glycolic pathway increased malic acid production. Accordingly, genes of mstC, hxkA, pfkA, and pkiA were overexpressed altogether in S895, and the resultant strain S1149 was constructed. The titer of malic acid in fed-batch fermentation with S1149 reached 201.13 g/L. Compared with S575, the byproduct of citric acid was completely abolished in S1149, and the ratio of malic acid/glucose was increased from 1.27 to 1.64 mol/mol, the highest yield reported so far, and the fermentation period was shortened from 9 to 8 days. Thus, a strain with great industrial application potential was developed by engineering nine genes in A. niger, and a pilot fermentation technology was exploited.

D-Xylonic Acid from Recombinant E. coli BL21 (DE3): Comparison between Shake Flask and Benchtop Bioreactor Fermentation

Production D-xylonic acid from recombinant E. coli BL21 (DE3) at a small scale has been successfully done several times. In an attempt to scale up the production process to a bigger scale, fermentation in bioreactor was conducted. The comparison on growth of recombinant E. coli BL21 (DE3) and production of D-xylonic acid in both shake flask and bioreactor was investigated. Higher specific growth rate of recombinant E. coli BL21 (DE3) and concentration of D-xylonic acid however, was obtained by fermentation in shake flask which is 0.273 h−1 and 9.06 gL−1 D-xylonic acid respectively. The result suggests several mistakes done during fermentation in bioreactor that causes low concentration of D-xylonic acid in bioreactor fermentation. Therefore, this calls up for improvement and better scale-up strategies in future work.

Study the Effect of pH on the Fermentation Anaerobic-Aerobic Siwalan (Borassus flabellifer L.) Sap to Produce Acetic Acid

This research is to study the effect of ethanol fermentation aerobic pH on acetic acid product. Anaerobic fermentation uses saccharomyces cerevisiae to produce ethanol, and aerobic fermentation uses acetobacter acetic for acetic acid production. In aerobic ethanol fermentation using pH 3; 3.5; 4 and 5. The ethanol concentration was evaluated using GC ULTRA Scientific Gas Chromatography, DSQ II detector, and MS 220 column. Acetic acid produced was analyzed using an alkalymetric method. Anaerobic fermentation uses Saccharomyces cerevisiae with 1-day log phase, while aerobic fermentation uses acetobacter aceti with a 5-day log phase. Fermentation using saccharomyces cerevisiae within 24 hours so that reduction sugar could stably decrease, optimum ethanol could be got at optimum pH 6 which could decrease 55 % of reducing sugar concentration to produce 8,20583 %v/v ethanol. Fermentation acetate acid content observed in 3 days at pH 6 and 30 ⁰C will produce 6,659 g/l also shows that pH 4-6 at 30 ⁰C will produce 6,605 g/l acetate acid. Aerobic fermentation of acetate acid in 3 days shows that pH 4-6 is highly affected by temperature at 30⁰C. Statistical analysis shows, in ethanol production pH and fermentation time give significant effect, but interaction has no significant effect.

High Performance Liquid Chromatography and Metabolomics Analysis of Tannase Metabolism of Gallic Acid and Gallates in Tea Leaves.

Tannase (E.C. 3.1.1.20) is hypothesized to be involved in the metabolism of gallates and gallic acid (GA) in pu-erh tea fermentation. In this work, we measured tannase in Aspergillus niger fermented tea leaves and confirmed the production of fungal tannase during pu-erh tea fermentation. A decrease in catechin and theaflavin gallates and a significant increase in GA content and the relative peak areas of ethyl gallate, procyanidin A2, procyanidin B2, procyanidin B3, catechin-catechin-catechin, epiafzelechin, and epicatechin-epiafzelechin [variable importance in the projection (VIP) > 1.0, p < 0.05, and fold change (FC) > 1.5] were observed using high performance liquid chromatography (HPLC) and metabolomics analysis of tea leaves fermented or hydrolyzed by tannase. In vitro assays showed that hydrolysis by tannase or polymerization of catechins increased the antioxidant activity of tea leaves. In summary, we identified a metabolic pathway for gallates and their derivatives in tea leaves hydrolyzed by tannase as well as associated changes in gallate and GA concentrations caused by fungal tannase during pu-erh tea fermentation.

An Economical Method for Simultaneously Improving Pretreatment and Anaerobic Fermentation Effects on Corn Straw Using Ultra-Low Concentration FeCl2

Low pollution, slight corrosion, and low cost are the main challenges in the conversion of biomass to biogas. In this work, based on the whole process optimization of biomass conversion, an effective method using an ultra-low concentration of FeCl2 was proposed to simultaneously promote the biochemical reaction and improve the pretreatment effect. The concentration of FeCl2 in the pretreatment was determined according to the requirements of the minimum amount which led to the optimal performance of the anaerobic system and had economical importance. The effects of FeCl2 in the pretreatment and anaerobic fermentation were evaluated by comparing with that of distilled water in the production of hydrolysis products and organic acids. The optimal condition was obtained at 180 °C and 10 min with 1 × 10−5 mol/L FeCl2 pretreatment. At that condition, hemicellulose achieved a high conversion of 97.6%, and the released xylose reached nearly 95%. At least 77.5% of the organic matter in the solution can be utilized for subsequent fermentation. FeCl2 pretreatment also accelerated the anaerobic acidification fermentation process and promoted organic acid yields. The work provided a meaningful and economical choice for the conversion technology of biomass to biogas.