Optimization Of Fermentation Parameters Research Articles

Utilization of molasses Wastewater for enzymatic fermentation in bioethanol production and residual glucose recovery

Molasses liquid waste (MLW) is a byproduct of the bioethanol production process from sugar cane molasses, typically containing approximately 10 % v/v glucose. This study investigates the use of enzymatic fermentation with turbo yeast to enhance bioethanol production from MLW while minimizing fermentation time. Various volumes of MLW, ranging from 500 to 2500 mL, were pretreated to remove impurities and then stirred for 30 min prior to fermentation. Fermentation was carried out using turbo yeast concentrations of 2 to 6 % v/v over durations of 4 to 12 days, with the pH maintained at 4.5 to achieve a bioethanol content of 21.92 % v/v. Optimization of the fermentation process was performed using Response Surface Methodology (RSM). Results indicated that an optimized condition of 3 % v/v turbo yeast and an 8-day fermentation period yielded the highest bioethanol content while minimizing residual glucose to approximately 2.04 % v/v. These findings provide valuable insights for optimizing fermentation parameters to maximize bioethanol yield from MLW.

Reprogramming Yarrowia lipolytica metabolism for efficient synthesis of itaconic acid from flask to semipilot scale.

Itaconic acid is an emerging platform chemical with extensive applications. Itaconic acid is currently produced by Aspergillus terreus through biological fermentation. However, A. terreus is a fungal pathogen that needs additional morphology controls, making itaconic acid production on industrial scale problematic. Here, we reprogrammed the Generally Recognized As Safe (GRAS) yeast Yarrowia lipolytica for competitive itaconic acid production. After preventing carbon sink into lipid accumulation, we evaluated itaconic acid production both inside and outside the mitochondria while fine-tuning its biosynthetic pathway. We then mimicked the regulation of nitrogen limitation in nitrogen-replete conditions by down-regulating NAD+-dependent isocitrate dehydrogenase through weak promoters, RNA interference, or CRISPR interference. Ultimately, we optimized fermentation parameters for fed-batch cultivations and produced itaconic acid titers of 130.1 grams per liter in 1-liter bioreactors and 94.8 grams per liter in a 50-liter bioreactor on semipilot scale. Our findings provide effective approaches to harness the GRAS microorganism Y. lipolytica for competitive industrial-scale production of itaconic acid.

Conjugated Linoleic Acid Production in Pine Nut Oil: A Lactiplantibacillus plantarum Lp-01 Fermentation Approach.

Conjugated linoleic acid (CLA) is a class of bioactive fatty acids that exhibit various physiological activities such as anti-cancer, anti-atherosclerosis, and lipid-lowering. It is an essential fatty acid that cannot be synthesized by the human body and must be derived from dietary sources. The natural sources of CLA are limited, predominantly relying on chemical and enzymatic syntheses methods. Microbial biosynthesis represents an environmentally benign approach for CLA production. Pine nut oil, containing 40-60% linoleic acid, serves as a promising substrate for CLA enrichment. In the present study, we developed a novel method for the production of CLA from pine nut oil using Lactiplantibacillus plantarum (L. plantarum) Lp-01, which harbors a linoleic acid isomerase. The optimal fermentation parameters for CLA production were determined using a combination of single-factor and response surface methodologies: an inoculum size of 2%, a fermentation temperature of 36 °C, a fermentation time of 20 h, and a pine nut oil concentration of 11%. Under these optimized conditions, the resultant CLA yield was 33.47 μg/mL. Gas chromatography analysis revealed that the fermentation process yielded a mixture of c9, t11CLA and t10, c12 CLA isomers, representing 4.91% and 4.86% of the total fatty acid content, respectively.

Harnessing Fermented Soymilk Production by a Newly Isolated Pediococcus acidilactici F3 to Enhance Antioxidant Level with High Antimicrobial Activity against Food-Borne Pathogens during Co-Culture.

In this study, a newly isolated Pediococcus acidilactici F3 was used as probiotic starter for producing fermented soymilk to enhance antioxidant properties with high antimicrobial activity against food-borne pathogens. The objectives of this study were to investigate optimized fermentation parameters of soymilk for enhancing antioxidant property by P. acidilactici F3 and to assess the dynamic antimicrobial activity of the fermented soymilk during co-culturing against candidate food-borne pathogens. Based on central composite design (CCD) methodology, the maximum predicted percentage of antioxidant activity was 78.9% DPPH inhibition. After model validation by a 2D contour plot, more suitable optimum parameters were adjusted to be 2% (v/v) inoculum and 2.5 g/L glucose incubated at 30 °C for 18 h. These parameters could provide the comparable maximum percentage of antioxidant activity at 74.5 ± 1.2% DPPH inhibition, which was up to a 23% increase compared to that of non-fermented soymilk. During 20 days of storage at 4 °C, antioxidant activities and viable cells of the fermented soymilk were stable while phenolic and organic contents were slightly increased. Interestingly, the fermented soymilk completely inhibited food-borne pathogens, Salmonella Typhimurium ATCC 13311, and Escherichia coli ATCC 25922 during the co-culture incubation. Results showed that the soymilk fermented by P. acidilactici F3 may be one of the alternative functional foods enriched in probiotics, and the antioxidation and antimicrobial activities may retain nutritional values and provide health benefits to consumers with high confidence.

Optimization of fermentation parameters and their impact on the final properties of the cereal-legume-based fermented product

The enhancement of food diversification through the utilization of underutilized crops is imperative at both national and household levels due to their inherent high nutritional value. Employing fermentation technology stands out as a promising approach for processing these crops at the household scale. Fermented foods exhibit attributes conducive to maintaining a healthy dietary regimen, as they are abundant in nutrients, cost-effective, easy to produce, and serve as potent sources of proteins and other essential dietary components for alleviating protein malnutrition, particularly in children. In the current study, experiments were conducted to standardise the process for formulating idli batter using blends of barnyard millet, black gram, and black soybean, employing fermentation technology. The experimental design followed the Box-Behnken approach, encompassing three levels of predicted variables: particle size (400, 500, and 600 μ), temperature (28, 32, and 36 °C), and fermentation time (8, 10, and 12 h). Various properties of the resultant idli batter influenced by fermentation parameters, including batter volume, pH, titratable acidity, and density, were meticulously examined. The observed batter volume ranged from 1 to 67 mL, pH from 5.7 to 4.58, titratable acidity from 0.36 to 0.67%, and density from 1.09 to 0.63 g/cm3. The optimal particle size of 400 μ, coupled with a fermentation temperature of 34.5 °C and a fermentation time of 12 h, yielded maximal expansion in batter volume, thereby contributing to the preparation of idli of superior quality. Additionally, the fermentation kinetics of the optimized batter were investigated to elucidate the growth patterns of microorganisms involved in the fermentation process.

Current trends in medium‐chain‐length polyhydroxyalkanoates: Microbial production, purification, and characterization

AbstractPolyhydroxyalkanoates (PHAs) have gained interest recently due to their biodegradability and versatility. In particular, the chemical compositions of medium‐chain‐length (mcl)‐PHAs are highly diverse, comprising different monomers containing 6–14 carbon atoms. This review summarizes different feedstocks and fermentation strategies to enhance mcl‐PHA production and briefly discusses the downstream processing. This review also provides comprehensive details on analytical tools for determining the composition and properties of mcl‐PHA. Moreover, this study provides novel information by statistically analyzing the data collected from several reports on mcl‐PHA to determine the optimal fermentation parameters (specific growth rate, PHA productivity, and PHA yield from various structurally related and unrelated substrates), mcl‐PHA composition, molecular weight (MW), and thermal and mechanical properties, in addition to other relevant statistical values. The analysis revealed that the median PHA productivity observed in the fed‐batch feeding strategy was 0.4 g L−1 h−1, which is eight times higher than that obtained from batch feeding (0.05 g L−1 h−1). Furthermore, 3‐hydroxyoctanoate and ‐decanoate were the primary monomers incorporated into mcl‐PHA. The investigation also determined the median glass transition temperature (−43°C) and melting temperature (47°C), which indicated that mcl‐PHA is a flexible amorphous polymer at room temperature with a median MW of 104 kDa. However, information on the monomer composition or heterogeneity and the associated physical and mechanical data of mcl‐PHAs is inadequate. Based on their mechanical values, the mcl‐PHAs can be classified as semi‐crystalline polymers (median crystallinity 23%) with rubber‐like properties and a median elongation at break of 385%. However, due to the limited mechanical data available for mcl‐PHAs with known monomer composition, identifying suitable processing tools and applications to develop mcl‐PHAs further is challenging.

Batch fermentation kinetics study of biosynthesis lipopeptides by Bacillus altitudinis Q7 in 5 L fermenter

Optimization of fermentation parameters can effectively increase microbial metabolites. The fermentation conditions of biosynthesis lipopeptides by Bacillus altitudinis Q7 (B. altitudinis Q7) in 5 L reactor were optimized and the fermentation kinetics were monitored throughout the fermentation process. By design-response surface methodology, the results showed that under optimal conditions (72 h, pH 6.6, 31 °C, 3% inoculum, 200 rpm, 1.5 L/min aeration), the lipopeptide yield reached 1.689 mg/mL, 24.5% higher than under single-factor conditions, with maximum biomass dry weight of 1.650 g/L. According to the logistic and Luedeking-Piret approximate models, kinetic equation models of growth, product (lipopeptide) synthesis, and substrate (glucose) utilization during the fermentation process were simulated. This was done to fit variables and devise optimal control strategies. The research has improved the yield of target products in fermentation processes, reduced production costs and provided a theoretical basis for the simulation, optimisation and regulation of fermentation in modern industry.

Methane fermentation to methanol (biological gas‐to‐liquid process) usingMethylotuvimicrobium buryatense5GB1C

AbstractMethanol is a potential alternate liquid transportation fuel for blending with gasoline. Biochemical conversion of methane to methanol is a green process for methanol production. This paper reports biochemical methanol production using type I γ‐proteobacteriaMethylotuvimicrobium buryatense, which has particular importance from the viewpoint of scalable biological gas to liquid processes for industrial application. A statistical design of experiments (at the serum bottle level) was used to optimize fermentation parameters. Enhancement in methanol accumulation was attempted using methanol dehydrogenase inhibitors. This was followed by a validation experiment run in a bioreactor at optimum conditions. At optimum conditions (pH = 7, phosphate concentration = 140 mM, temperature = 25°C) and optical density (600 nm) of 0.3, a methanol titer of 8.54 mM was achieved in 24 h (methane conversion = 20.8%). The addition of a methanol dehydrogenase inhibitor (0.5 mM Ethylenediaminetetraacetic acid) enhanced the methanol concentration to 10.37 mM. Experiments in a 3.7 L bioreactor using 1.68 bar headspace pressure and optical density (600 nm) of 0.1 yielded 23.7 mM methanol in 24 h (methane conversion = 47.8%). The methanol titers obtained usingM. buryatense5GB1C in 24 h fermentation are significantly higher than several previously reported methanotrophs. These results demonstrate the potential ofM. buryatense5GB1C for the biochemical synthesis of methanol.

Optimization of limonin invertase production by scaling up aspergillus tabingensis UA13 fermentation to a 5-liter scale.

The enzymatic approach is a highly effective and the major scientific method to eliminating bitter components in citrus-derived products nowadays. Microbial production of limonin invertase stands out due to its pivotal role in the removal of the bitter substance, limonin. The optimization of fermentation parameters and the study of scale-up fermentation are imperative for product commercialization. In this study, we focused on optimizing stirring speed, fermentation temperature, and initial pH to enhance the growth and limonin invertase production by the Aspergillus tabin (A. tabin) strain UA13 in a 5-liter stirred-tank bioreactor. Our results revealed the following optimal parameters are: a stirring speed of 300rpm, a fermentation temperature of 35 °C and a pH 5.0. Under these optimized conditions, the limonin invertase activity reached its peak at 63.38U mL-1, representing a 1.67-fold increase compared to the unoptimized conditions (38.10U mL-1), while also reducing the fermentation duration by 12 hours. Furthermore, our research demonstrated that limonin invertase effectively hydrolyze limonin in grapefruit juice, reducing its content from 13.28μg mL-1 to 2.14μg mL-1, as determined by HPLC, resulting in a 6.21-fold reduction of the bitter substance.

Optimization of Bioethanol Production from <em>Ceratophyllum demersum</em> for hand sanitizers

Hands are the primary way to spread microorganisms, thus hand washing is the primary defence and an essential element of personal hygiene for infection control. Hand sanitizers that contain ethanol as their main constituent are used to kill a broad range of microbes. Bioethanol production has relied heavily on the use of first-generation feedstock. Therefore, the development and utilization of alternative feedstocks such as weed (Ceratophyllum demersum) and other non-food crops have gained more attention in recent times. This study explores the bioethanol production using C. demersum, a weedy species, for its potential use in hand sanitizer production. The substrate, C. demersum was subjected to mechanical pre-treatment and then pre-treated with varying concentrations of sulfuric acid, which was subsequently followed by enzymatic pre-treatment and allowed for fermentation using Saccharomyces cerevisiae. The results showed that a sulfuric acid concentration of 1 M resulted in a significantly higher amount of reducing sugar and alcohol yield compared to other concentrations, and this was selected for further studies. After optimization of fermentation parameters, a significantly higher alcohol yield of 2.6% was achieved using a S. cerevisiae inoculum concentration of 100 g/l and agitation at 150 rpm at 40°C for 36 hours. Subsequent optimization of fermentation media components further increased the alcohol yield to 3.7%, with the use of 6 g/l yeast extract, 6 g/l (NH4)2SO4, 5 g/l MgSO4, and 8 g/l KH2PO4. The resulting alcohol mixture was analyzed and found to contain 84.9% bioethanol. An agar well diffusion assay was conducted against bacteria and fungi. The results showed that all the bacterial and fungal strains were sensitive to the bioethanol extract as evidenced by the presence of an inhibition zone.

The effects of Trametes versicolor fermented Rosa roxburghii tratt and coix seed quild on the nutrition, sensory characteristics and physical and chemical parameters of yogurt

Trametes versicolor can produce aromatic flavor in growth and development, widely used in food fermentation. This study used a One-Factor-at-a-Time (OFAT) test and response surface analysis to study the optimum fermentation parameters of Rosa roxburghii tratt and coix seed yogurt by Trametes versicolor. The best fermentation process is as follows: skim milk powder 17 %, sucrose content 4 %, Rosa roxburghii tratt and coix seed liquid 36 %, fermentation temperature 39 °C, inoculum 2 %, strain ratio 2:1:1(LB12: BLH1: Q-1), fermentation time 9.5 h. Under this fermentation process, the sensory score was 82.11, the contents of vitamin C, GABA, and total live bacteria in this yogurt were 13.89, 2.58, and 1.02 times higher than in common yogurt. Correlation analyses showed a significant contribution of the leavening agent to the GABA content of yogurt. This study provides a foundation for producing Rosa roxburghii tratt and coix seed yogurt with high sensory and nutritional value.

Optimization of the Fermentation Conditions of Huaniu Apple Cider and Quantification of Volatile Compounds Using HS-SPME-GC/MS.

The fermentation process and composition of volatile compounds play a crucial role in the production of Huaniu apple cider. This study aimed to optimize the fermentation conditions of Huaniu apple cider and quantify its volatile compounds using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS). The optimal fermentation parameters were determined using response surface methodology (RSM). The optimal fermentation temperature was 25.48 °C, initial soluble solids were 18.90 degrees Brix, inoculation amount was 8.23%, and initial pH was 3.93. The fermentation rate was determined to be 3.0, and the predicted value from the verification test was 3.014. This finding demonstrated the excellent predictability of a RSM-optimized fermentation test for Huaniu apple cider, indicating the reliability of the process conditions. Moreover, the analysis of volatile compounds in the optimized Huaniu cider identified 72 different ingredients, including 41 esters, 16 alcohols, 6 acids, and 9 other substances. Notably, the esters exhibited high levels of ethyl acetate, ethyl octanoate, and ethyl capricate. Similarly, the alcohols demonstrated higher levels of 3-methyl-1-butanol, phenethylethanol, and 2-methyl-1-propanol, while the acids displayed increased concentrations of acetic acid, caproic acid, and caprylic acid. This study provides the essential technical parameters required for the preparation of Huaniu apple cider while also serving as a valuable reference for investigating its distinct flavor profile.

Optimization of the Process for Green Jujube Vinegar and Organic Acid and Volatile Compound Analysis during Brewing.

Healthy fruit vinegar has become very popular recently in China. This study aimed to produce fruit vinegar with a good taste, high nutritional value, and strong functional properties from green jujube. This study investigated the optimization of the process for green jujube vinegar using response surface methodology. The optimum fermentation parameters for green jujube vinegar were determined as follows: initial alcoholicity 6%, acetobacter 8%, fermentation temperature 32 °C, and time 7 d. The organic acids of the optimized sample were evaluated by HPLC, and the volatile substances were identified and analyzed by HS-SPME and GC-MS during the fermentation and aging of the green jujube vinegar. The results showed that the variation trends of the different organic acids during the making of the green jujube vinegar were significantly different. Organic acids are the key flavor compounds of green jujube vinegar, and their changes were mainly attributed to microbial metabolism. In particular, the green jujube vinegar stood out in terms of volatile aroma compounds, including a total of 61 volatile compounds whose major components were acetic acid, isoamyl acetate, ethyl acetate, 3-hydroxy-2-butanone, methyl palmitate, and ethanol. The results can provide theoretical support for the production of green jujube vinegar.

Response surface methodology for the mixed fungal fermentation of Codonopsis pilosula straw using Trichoderma reesei and Coprinus comatus.

The objective of this study was to investigate the cellulose degradation rate (CDR) and lignin degradation rate (LDR) of Codonopsis pilosula straw (CPS) and the optimal fermentation parameters for mixed fungal fermentation. Single-factor tests were used to study the effects of the fungal ratio (Trichoderma reesei: Coprinus comatus), fungal inoculum, corn flour content, and fermentation time on the degradation rate of cellulose and lignin. Based on the results of this experiment, the optimal fermentation factors were identified, and the effects of various factors and their interactions on the degradation rates of cellulose and lignin were further evaluated using the response surface method. The quadratic polynomial mathematical model of degradation rates of the cellulose and lignin in CPS by mixed fungus fermentation was established using Design Expert software v8.0.6. Under the optimal parameters for fungal fermentation of CPS straw (fungal ratio 4:6, fungal inoculum 8%, corn flour content 10%, fermentation time of 15 d), the CDR and LDR reached 13.65% and 10.73%, respectively. Collectively, the mixed fungal fermentation of CPS resulted in decreased lignin and cellulose content, better retention of nutrients, and enhanced fermentation quality. The results of this study indicate that fermentation using Trichoderma reesei and Coprinus comatus is a productive method for straw degradation, providing a theoretical basis for the development of CPS as feed.

Phytochemical and Structural Changes of Chickpea Beverage Prepared Using Ultrasound-Assisted Fermentation with Optimized Ultrasound Parameters Modelled by Response Surface Methodology

To improve the quality of fermented chickpea beverages, a highly nutritious substitute for dairy, the Box-Behnken design and the response surface methodology were used to obtain optimized ultrasonic parameters for producing ultrasound-assisted fermented chickpea beverages. The determining parameters were the lactic acid, reducing sugar content, and the cell viability of the treated product. The most significant parameters obtained were frequency and treatment duration, while power density was relatively insignificant. The optimum fermentation parameters obtained were a treatment start time of 3 h, treatment duration of 80 min, frequency of 27.5 kHz, and power density of 100 W/L with optimum yields of 0.23096 mg/mL, 2.92898 mg/mL, and 0.488189 for reducing sugar, lactic acid, and cell viability index, respectively, with desirability above 0.95. Further analysis of the ultrasound treatment’s effect on the product’s structure showed the ultrasound-assisted fermented chickpea beverage was more structurally stable and homogenous, with even distribution of macromolecules present.

Optimization of fermentation, purification and properties of blue pigment produced from Quambalaria cyanescens QY229.

Blue pigments have broad applications in foods, cosmetics, and clothing. However, natural blue pigments are rare. At present, the majority of blue pigments for sale are chemically synthetic. Owing to the safety risks of chemical pigments, it is an urgent demand to develop novel natural blue pigments. The fermentation medium and culture conditions of blue pigment produced by Quambalaria cyanescens QY229 were optimized by Plackett-Burman (PB) experimental design and response surface methodology (RSM) for the first time. The stability, bioactivity and toxicity of the obtained blue pigment were studied after isolation and purification. The results showed that the optimal fermentation parameters were 34.61 g·L-1 of peptone concentration, 31.67°C of growing temperature, and 72.33mL of medium volume in a 250mL flask, and the yield of blue pigment reached 348.2±7.1 U·mL-1. QY229 blue pigment is stable to light, heat, pH, most metal ions and additives, and has certain antioxidant and inhibitory activity of α-glucosidase in vitro. QY229 blue pigment at concentrations of 0-1.25mg·mL-1 was nontoxic to Caenorhabditis elegans in an acute toxicity trial.

Fermentative processing of unexploited fruit, karonda (Carissa carandus L.) into alcoholic beverages

Karonda (Carissa carandus L.) is an underexploited fruit rich in bioactive compounds and is well-known for its therapeutic and nutraceutical potential. The ripe fruits are highly perishable in nature due to which a fermentative process may be exploited for retention of its bioactive compounds. In the present study, two variables i.e. total soluble solids (oBx) and juice content (% v/v) were standardized for the development of fermented alcoholic beverages using Saccharomyces cerevisiae MTCC 11,815 from ripe fruits of two karonda genotypes i.e. white with pink blush and green with purple blush. The alcoholic beverages prepared under optimized conditions were further subjected to organoleptic evaluation. The results revealed that the optimized fermentation parameters i.e. total soluble solids and juice content are 20 oBx and 51.712% (w/v) and 15.5 oBx and 30% (w/v) for white with pink blush and green with purple blush, respectively, which were further confirmed through validation experiments. The alcohol content of karonda beverages varied from 4.55 to 5.56%. The fermented alcoholic beverages were also found to retain ascorbic acid (mg/100 ml), phenolics (mg/100 ml) and antioxidants (% DPPH scavenging activity) as 24.5 and 28.5; 17.9 and 15.0; 84.85 and 81.05, respectively, among white with pink blush and green with purple blush. The organoleptic evaluations of the fermented beverages from both genotypes were rated as “liked very much”. The present study thus aids in the promising potential of fermentative processing of karonda to harness bioactives in the fruit, thereby, contributing to food and nutritional security.

Optimization of Spontaneous Fermentation Conditions of Kohlrabi by Response Surface Methodology

Kohlrabi is a valuable crop due to its substantial amount of macro- and micronutrients. It is mostly consumed in fresh form, as jam or fermented product. This current work aimed to optimize the spontaneous fermentation conditions of kohlrabi in order to improve its product functionality and diversity. For this purpose, a Box Behnken design was employed to evaluate the effects of boiling time (0–8 min.), vinegar ratio (0–50%), and salt content (2–8%) on chemical and microbiological properties of fermented kohlrabi. Some chemical and microbiological analyses, including total phenolic content, total antioxidant capacity, total acidity, pH, salt content, total counts of yeast and molds, and mesophilic and lactic acid bacteria, were determined. The total antioxidant capacity of samples changed between 11.91 and 75.75 µmol Trolox/100 g, respectively. Both ANOVA results (p < 0.05) and PCA model (R2 = 0.99; Q2 = 0.72) confirmed that boiling time is the important factor affecting the fermentation process. The optimal fermentation parameters for kohlrabi were determined to be 44.12% vinegar and 2.07% salt concentrations without the boiling step by response surface methodology.

Production of itaconic acid from sweet potato (Ipomoea batata) peel using naturally occurring fungi in solid state fermentation

This study evaluates the potentials of sweet potato peel as a substrate for itaconic acid production in solid state fermentation using naturally occurring fungi. Sweet potato peel was analyzed for proximate composition using standard methods. Fungi were obtained from the peel by solid state fermentation and identified using microscopic and molecular methods. Fermentation for itaconic acid production was done using isolated fungus and Aspergillus niger (ATCC 16888) was used as control. Optimization of fermentation parameters was carried out using standard procedures. Assay for itaconic acid and total titratable acidity (TTA) were analyzed using standard methods. Reducing sugar was obtained using DNSA method. Proximate composition of the peel reveals carbohydrate content to be 79%, protein, 5% and ash, 4%. Fungus isolated was identified as Aspergillus flavus L-2482/2012. Highest itaconic acid production by A. flavus was 7.74±0.00 mg/ml on day 5 at 30 g substrate concentration. Using 2 ml of 1 x 107 spores/ml, A. flavus and A. niger produced 6.97±0.13 and 6.67±0.09 mg/ml respectively. Optimum temperature for itaconic acid production was 30°C for A. niger and A. flavus. TTA ranged between 0.04±0.00 to 0.21±0.01 and 0.05±0.00 to 0.26±0.00 mg/ml for A. niger and A. flavus respectively. The highest reducing sugar, 0.51±0.00 mg/ml was obtained at substrate concentration 40 mg/ml on day 5 by A. flavus while A. niger had reducing sugar value of 0.37±0.00 mg/ml. In conclusion, A. flavus L-2482/2012. has great potentials for itaconic acid production using sweet potato peel in solid state fermentation under optimized conditions.

Variation in microbiological heterogeneity in Chinese strong-flavor Baijiu fermentation for four representative varieties of sorghum

The quality and composition of strong-flavor Baijiu (SFB), a type of Chinese liquor, depends on the variety of sorghum used in fermentation. However, comprehensive in situ studies measuring the effects sorghum varieties on the fermentation are lacking and the underlying microbial mechanisms remains poorly understood. We studied the in situ fermentation of SFB by using metagenomic, metaproteomic, and metabolomic techniques across four sorghum varieties. Sensory characteristics were best for SFB made from glutinous variety Luzhouhong, followed by glutinous hybrid Jinnuoliang and Jinuoliang, and those made with non-glutinous Dongzajiao. In agreement with sensory evaluations, the volatile composition of SFB samples differed between sorghum varieties (P < 0.05). Fermentation of different sorghum varieties varied in microbial diversity, structure, volatile compounds, and physicochemical properties (pH, temperature, starch, reducing sugar, and moisture) (P < 0.05), with most changes occurring within the first 21 days. Additionally, the microbial interactions and their relationship with volatiles, as well as the physicochemical factors that govern microbial succession, differed between varieties of sorghum. The number of physicochemical factors affecting bacterial communities outweighed those affecting fungal communities, suggesting that bacteria were less resilient to the brewing conditions. This correlates with the finding that bacteria play a major role in the differences in microbial communities and metabolic functions during fermentation with the different varieties of sorghum. Metagenomic function analysis revealed differences in amino acid and carbohydrate metabolism between sorghum varieties throughout most of the brewing process. Metaproteomics further indicated most differential proteins were found in these two pathways, related to differences in volatiles between sorghum varieties of Baijiu and originating from Lactobacillus. These results provide insight into the microbial principles underlying Baijiu production and can be used to improve the quality of Baijiu by selecting the appropriate raw materials and optimizing fermentation parameters.