Glucoamylase Activity Research Articles

Effects of Medium Chain Triglycerides Intake on Lipid Metabolism and Intestinal Disaccharidase Activities in Rats

It has been reported that medium-chain triglyceride (MCT) have various physiological functions, such as anti-obesity and hypolipidemic effects. They can also elicit increased disaccharidase activity and intestinal cell proliferation. However, a meta-analysis of randomized controlled trials, comparing the effects of MCT on weight loss and body composition, detected commercial bias. Additional research on the physiological functions is needed in order to have conclusive evidence. Thus, we sought to evaluate the various functions of MCT by conducting a feeding study in rats. Rats fed a diet containing 15% (w/w) MCT, had significantly lower visceral fat weight, plasma and liver lipid concentrations; they had significantly higher intestinal maltase and glucoamylase activities; and they had a greater number of Ki-67 positive cells/crypt, compared to the rats fed a diet containing 15% (w/w) lard. The effects of a diet containing 5% (w/w) MCT was observed only for plasma cholesterol levels and the number of Ki-67 positive cells/crypt; in which some results were found to be inconsistent with previous reports. These results indicate that physiological functions of MCT are numerous and need to be confirmed by additional research.

Effects of the degree of milling on the quality characteristics of rice ‘Nuruk’

This study aimed to investigate the effects of the degrees of milling of rice (0-50%) on the physicochemical properties and enzymatic activities of rice ‘Nuruk’. As results, the contents of the general components of milled rice, except for the starch value (85.13-90.99%) decreased as the degree of milling increased. The moisture content of rice with different degrees of milling ranged from 11.04 to 12.68% and significantly decreased as the degree of milling increased. Furthermore, the hydration rate increased as the degree of milling increased. The pH of rice ‘Nuruk’ was the lowest at 5.32 in the 0% milled rice ‘Nuruk’ and highest at 5.98 in the 30% milled one, which indicated no correlation between pH and degree of milling. By contrast, the soluble solid and reducing sugar contents which are correlated with the starch value of rice increased as the degree of milling increased. For the enzymatic activities of each rice ‘Nuruk’, there was no clear trend for the α-amylase and acidic protease activities with respect to the degree of milling, whereas the glucoamylase activity decreased with increasing degree of milling. Correlation analyses indicated that the activity of glucoamylase decreased as the starch value of rice increased, but increased as the crude protein content of rice increased. The activity of acidic protease had a negative correlation with the crude lipid content of rice.

Solid-State Fermentation of Agroindustrial Residues for Glucoamylase Production from Endophytic Fungi Penicillium javanicum of Solanum tuberosum L.

Glucoamylase production has been evaluated under solid-state fermentation of agro-industrial residues including groundnut shell, corncob, corn stover, sugarcane bagasse, wheat straw, barely straw and rice straw as renewable cheap substrates by different 14 endophytic fungal species. Among them the endophytic fungi Penicillium javanicum obtained from the root of Solanum tuberosum L. showed the maximum yield of glucoamylase using groundnut shell as solid substrate (289.23 ± 0.80 U/gds). Under the optimized production parameters in solid state fermentation process (250 mL Erlenmeyer flask containing 20 grams groundnut shell supplemented with 30% soya waste as an inexpensive, eco-friendly way of enzyme production sieved to 1mm, moistened to 55% initial moisture content with potato process wastewater, pH 5.0, inoculum intense 2 × 108 spore and incubated at 30°C for 5 days fermentation period), a fourfold increase (4.19-fold) in glucoamylase production was occurred. In our study there was a strong relation between the enzyme secretion and the trophophase. The purified enzyme exhibited specific activity 81.60 and 237. 24 U/mg with enzyme recovery equal to 51.11 and 22.14% and purification fold 2.2 and 6.39-fold after the precipitation with (NH4)2SO4 and gel fractionation on sephadex G-100, respectively with maximum activity at 40-50°C and pH 5 and it was stable and retained 100% of its activity at temperature up to 60°C along with pH 5–7. The enzyme was not metallo enzyme due to EDTA and EGTA at 50 mM had no effect on glucoamylase activity but it was considered as a serine protease due to it lost 68 and 92% of its activity the serine protease inhibitor paramethyl sulfonyl fluoride (PMSF) at 10 and 50 mM, respectively.

Microbiota stratification and succession of amylase-producing Bacillus in traditional Chinese Jiuqu (fermentation starters).

Jiuqu are vital saccharifying and fermenting agents for Chinese fermented foods. Natural ventilation during Jiuqu fermentation causes changes in temperature, oxygen and moisture content, resulting in mass and heat gradients from the outer to inner areas of Jiuqu blocks. In the present study, microbiota stratification in Jiuqu was investigated by single molecule real-time sequencing and culture isolation. The contributors of Bacillus to amylase activity of Jiuqu and the dynamics of their biomass during Jiuqu fermentation were also analyzed. The dominant orders, genera and species between the inner and outer layers of Huangjiu qu (HJQ) were similar, although they displayed greater variance in two layers of Baijiu qu (BJQ). Bacillus possessed the highest diversity (including 27 species) in Jiuqu. Bacillus licheniformis, Bacillus altitudinis, Bacillus subtilis, Bacillus amyloliquefaciens and Bacillus megaterium were most prevalent in HJQ, whereas B. licheniformis, B. amyloliquefaciens and Bacillus cereus were dominant in BJQ. Isolates of B. amyloliquefaciens, B. subtilis and B. cereus exhibited high activities of amylase and glucoamylase. Quantification of Bacillus members possessing genes of α-amylase revealed that B. cereus and B. licheniformis were the most dominant microbes to secret α-amylase in Jiuqu and their biomass were increasing during Jiuqu fermentation. The present study demonstrates the microbial distribution in different layers of Jiuqu and clarifies the Bacillus species processing the activity of α-amylase. These results will help industries control the quality of Jiuqu by rationally selecting starters and optimizing their microbiota. © 2020 Society of Chemical Industry.

Improving cytosolic aspartate biosynthesis increases glucoamylase production in Aspergillus niger under oxygen limitation

BackgroundGlucoamylase is one of the most industrially applied enzymes, produced by Aspergillus species, like Aspergillus niger. Compared to the traditional ways of process optimization, the metabolic engineering strategies to improve glucoamylase production are relatively scarce.ResultsIn the previous study combined multi-omics integrative analysis and amino acid supplementation experiment, we predicted four amino acids (alanine, glutamate, glycine and aspartate) as the limited precursors for glucoamylase production in A. niger. To further verify this, five mutants namely OE-ala, OE-glu, OE-gly, OE-asp1 and OE-asp2, derived from the parental strain A. niger CBS 513.88, were constructed respectively for the overexpression of five genes responsible for the biosynthesis of the four kinds of amino acids (An11g02620, An04g00990, An05g00410, An04g06380 and An16g05570). Real-time quantitative PCR revealed that all these genes were successfully overexpressed at the mRNA level while the five mutants exhibited different performance in glucoamylase production in shake flask cultivation. Notably, the results demonstrated that mutant OE-asp2 which was constructed for reinforcing cytosolic aspartate synthetic pathway, exhibited significantly increased glucoamylase activity by 23.5% and 60.3% compared to CBS 513.88 in the cultivation of shake flask and the 5 L fermentor, respectively. Compared to A. niger CBS 513.88, mutant OE-asp2 has a higher intracellular amino acid pool, in particular, alanine, leucine, glycine and glutamine, while the pool of glutamate was decreased.ConclusionOur study combines the target prediction from multi-omics analysis with the experimental validation and proves the possibility of increasing glucoamylase production by enhancing limited amino acid biosynthesis. In short, this systematically conducted study will surely deepen the understanding of resources allocation in cell factory and provide new strategies for the rational design of enzyme production strains.

Duodenal Infusions of Starch with Casein or Glutamic Acid Influence Pancreatic and Small Intestinal Carbohydrase Activities in Cattle

Small intestinal starch digestion in ruminants is potentially limited by inadequate production of carbohydrases. Previous research has demonstrated that small intestinal starch digestion can be improved by postruminal supply of casein or glutamic acid. However, the mechanisms by which casein and glutamic acid increase starch digestion are not well understood. The objective of this experiment was to evaluate the effects of duodenal infusions of starch with casein or glutamic acid on postruminal carbohydrase activities in cattle. Twenty-two steers [mean body weight (BW) = 179±4.23kg] were surgically fitted with duodenal and ileal cannulas and limit-fed a soybean hull-based diet containing small amounts of starch. Raw cornstarch (1.61±0.0869kg/d) was infused into the duodenum alone (control), or with 118±7.21g glutamic acid/d, or 428±19.4g casein/d. Treatments were infused continuously for 58 d and then steers were killed for tissue collection. Activities of pancreatic (α-amylase) and intestinal (maltase, isomaltase, glucoamylase, sucrase) carbohydrases were determined. Data were analyzed as a randomized complete block (replicate group) design using the GLM procedure of SAS to determine effects of infusion treatment. Duodenal casein infusion increased (P <0.05) pancreatic α-amylase activity by 290%. Duodenal glutamic acid infusion increased (P <0.03) duodenal maltase activity by 233%. Duodenal casein infusion increased jejunal maltase (P=0.02) and glucoamylase (P=0.03) activity per gram protein by 62.9% and 97.4%, respectively. Duodenal casein infusion tended to increase (P=0.10) isomaltase activity per gram jejunum by 38.5% in the jejunum. Sucrase activity was not detected in any segment of the small intestine. These results suggest that small intestinal starch digestion can be improved in cattle with increased small intestinal flow of casein through increases in postruminal carbohydrase activities.

Isolation and Identification of Fungi with Glucoamylase Activity from Loog-pang-khao-mak (A Thai Traditional Fermentation Starter)

Isolation and Identification of Fungi with Glucoamylase Activity from Loog-pang-khao-mak (A Thai Traditional Fermentation Starter)

The improvement of glucoamylase production by UV irradiated strains of Aspergillus awamori KT-11

In many food industries, glucoamylase is extensively applied because of its ability to convert oligosaccharides into glucose. Recently, mutagenic treatments of Aspergillus awamori have been conducted to improve and enhance glucoamylase production. This research was focused on the study of glucoamylase production by strains of A. awamori after being exposed to ultra-violet (UV) irradiation. The parental strain was cultivated on the PDA plates and treated by exposing under UV lamp from 0 to 90 minutes with the time intervals of 30 min. Solid state fermentation was carried out to produce glucoamylase using cassava peel as a substrate. As compared to all strains, the mutant strain of A. awamori after being treated by 30 min of UV exposure time gave the highest activity of glucoamylase at 5.9 U/ml. The activity was two fold higher than the parental strain. The same mutant strain also reached its maximum value of total protein content at 97.31 µg/ml and 23% higher than parental strain. Glucoamylase production can be achieved and improved by the strain of A. awamori after UV mutagenic treatment.

Assessment of microbial quality and health risks associated with traditional rice wine starter Xaj-pitha of Assam, India: a step towards defined and controlled fermentation.

This study reports the microbial quality of ethnic starter culture Xaj-pitha used for rice wine fermentation in Assam. Here, we collected 60 Xaj-pitha samples belonging to Ahom community of the state and enumerated the microorganisms using spread plate technique. Illumina-based whole genome shotgun sequencing detected the presence of microbial contaminants like Acidovorax, Herbaspirillum, Methylobacterium, Pantoea, Pseudomonas, Stenotrophomonas, Staphylococcus, Micrococcus, Acinetobacter, etc. Presence of major health hazards associated with spontaneous rice wine fermentation necessitated method optimization through the development of a defined mixed starter culture. For this, functionally important α-amylase producers viz., Penicillium sp. ABTSJ23, Rhizopus oryzae ABTSJ63, Mucor guilliermondii ABTSJ72 and Amylomyces rouxii ABTSJ82 and eight yeasts viz., Saccharomyces cerevisiae ABTY1J, ABTY1S, ADJ5 & ADJ1,Wickerhamomyces anomalus ADJ2, Saccharomycopsis malanga ADJ3, Saccharomycopsis fibuligera ADJ4 and Saccharomycopsis malanga ADJ6 were retrieved using appropriate media. All the mould cultures tested negative for aflotoxins production. Among the yeasts, Saccharomyces cerevisiae ABTY1S and ADJ1 decarboxylated lysine HCl and tyramine HCl, respectively, indicating their biogenic amine production ability. For defined mixed starter culture, Amylomyces rouxii ABT82 with α-amylase (5.92U/ml) and glucoamylase (7.50U/ml) activities was selected as fungal partner; while Saccharomycopsis fibuligera ADJ4 and Saccharomyces cerevisiae ABT-Y1J with high ethanol production (up to 10.11% and 9.88% v/v, respectively) were selected as yeast partners. The mixed culture was able to produce high amount of glucose, ethanol and liquid (glucose 10.91% w/v; ethanol 7.5% w/v; liquid 51.0% w/v). Therefore, this study demonstrated the efficiency of mixed starter cultures for safe and controlled rice wine production.

Changes in the Activities of Alpha and Gluco-amylases during Malting of Some Improved Nigerian Sorghum Varieties

In this study changes in the alpha and glucoamylase activities of four different improved sorghum varieties were monitored over a 96-hour malting time to determine how the expression of the enzymes were affected by malting. Preliminary tests showed that SK5912 had the highest weight of 40 g/1000 grains and lowest malting loss of about 13%, while KSV 8 followed a weight of 36 g/1000 grains and the most malting loss of 22.6%. Enzyme results showed that the different sorghum varieties differed in their expression of the two of them across different malting regimes. However, all the varieties showed much higher expressions of glucoamylase than α-amylase at all the malting regime. Glucoamylase consistently showed its highest activities of over 71 U/ml across the four sorghum varieties after the first day of germination with variety SRNA giving the highest value slightly above 72 U/ml. The least glucoamylase activities were also given consistently across the four varieties by the unmalted raw grain. The highest α-amylase activities were generally shown across the four varieties after the third day of germination, with variety KSV 8 showing the highest value of about 14 U/ml. The control also gave the least α-amylase activities across all varieties with KSV8 giving the least. Considering the many important and multi-faceted roles that amylases are nowadays known to perform, the study of their expression dynamics in different plants and processes, one of which we report here, could help further the understanding of their characteristics and thus facilitate their maximal utilization.

PSIV-1 Effects of nutrient restriction and realimentation of gestating ewes on fetal carbohydrase activities in the small intestine

Abstract The small intestine plays an important role in post-ruminal carbohydrate digestion and there is limited information on its function in response to nutritional adaptation. To examine the effects of nutrient restriction and realimentation on fetal small intestinal carbohydrase activities during mid- to late-gestation, 41 singleton ewes (48.3±0.6 kg BW) were randomly assigned to dietary treatments: 100% (control; CON; n = 20) or 60% of nutrient requirements (restricted; RES; n = 21) from day 50–90 (mid-gestation) of gestation. At day 90, 14 ewes (CON, n = 7; RES, n = 7) were slaughtered. The remaining ewes were subjected to treatments of nutrient restriction or remained under a control diet from day 90–130 (late-gestation): CON-CON (n = 6), CON-RES (n = 7), RES-CON (n = 7), and RES-RES (n = 7) and were slaughtered at day 130. The fetal small intestine was weighed, subsampled, and assayed for carbohydrase (maltase, isomaltase, glucoamylase, lactase, and sucrase) activity. Enzyme activity was expressed as U/g and U/g protein. Protein concentration was expressed as mg/g intestine. Differences between means were determined using contrasts in the MIXED procedure of SAS. Small intestinal mass increased (P &amp;lt; 0.001) with day of gestation. Sucrase activity was undetected in the small intestine. Day of gestation did not affect carbohydrase development in the fetal small intestine. Nutrient restriction did not affect glucoamylase, maltase, or isomaltase activities. There was a significant mid-gestation treatment × late-gestation treatment interaction for lactase activity (P &amp;lt; 0.05). Realimentation during late-gestation after nutrient restriction during mid-gestation increased lactase activity in the fetal small intestine. These data demonstrate that fetal mucosal carbohydrases are imprinted early in gestation and brush border α-glycohydrolases involved in starch digestion (maltase, isomaltase, glucoamylase) do not respond to maternal nutrient restriction in sheep. Nutrient restriction of ewes during mid-gestation followed by realimentation during late-gestation may be a programming strategy to increase fetal lactase activity.

Isolasi dan Karakterisasi Amilase dari Kapang Alkalotoleran Asal Limbah Cair Tapioka

A total of 6 fungi isolates of growing at pH 9 and 2 isolates on pH 10 with amylolytic indexes 0f 0.07-1.42 have been isolated from cassava starch liquid waste. Two isolates having the highest amylolytic index were identified as Aspergillus sydowii K10 (1.42) and Aspergillus versicolor L30 (1.4). Both A. sydowii K10 and A. versicolor L30 were described as alcalotolerant for being able to grow with range pH 5-10. The optimal -amylases production of A. sydowii K10 and A. versicolor L30 was obtained after 4 and 3 days of incubation at 300C. The optimum of -amylase activity from A. sydowii K10 was at 400C and 700C, and pH 6; while those from A. versicolor L30 was at 500C and pH 6 respectively. Both A. sydowii K10 and A. versicolor L30 could produce glucoamylase. The optimum of glucoamylase activity from A. sydowii K10 was at 400C and pH 5, while those from A. versicolor L30 was at 500C and pH 5 respectively.

Characterization of sustained-release chitosan film loaded with rutin-β-cyclodextrin complex and glucoamylase.

Edible chitosan film incorporated with rutin-β-cyclodextrin was developed and characterized. The delivery of rutin was improved via the hydrolyzation function of glucoamylase, and the antioxidant activity of the chitosan film was enhanced by the addition of rutin. Sodium bicarbonate solution at different pHs (pH-adjusting reagent) was employed to afford the mild condition for the incorporated glucoamylase. The enzyme exhibited its hydrolyzation function to improve the release rate of rutin by destabilizing the rutin-β-cyclodextrin complex (RCC) in chitosan film. The optimum pH of glucoamylase was achieved with 5mL addition amount of 0.5mol/L sodium bicarbonate solution, and the glucoamylase improved the radical scavenging ratio of chitosan film. The yellowness of chitosan film was enhanced with the addition of RCC solution. The films prepared without water demonstrated coarse and rough surface, while the water-based films had smoother and even surface as examined by scanning electron microscopy. In contrast, these observations disappeared in the water immersion groups. X-ray diffraction suggested that the hydrolyzation of β-cyclodextrin and the interlinkage between β-cyclodextrin and the chitosan chain exerted a negative function on maintaining the crystal structure of pure chitosan film. Further, the destabilization of RCC complex with the glucoamylase activity was evidenced by the absence of peak associated with β-cyclodextrin as observed from Fourier transform infrared spectra. The enzyme improved the release of rutin and the addition of RCC successfully endowed antioxidant activity to the chitosan film.

Full recycling of citric acid wastewater through anaerobic digestion, air-stripping and pH control.

Anaerobic digestion effluent (ADE) from the anaerobic digestion treatment of citric acid wastewater can be reused as a potential substitute for process water in the citric acid fermentation. However, excessive sodium contained in ADE significantly decreases citric acid production. In this paper, the inhibition mechanism of sodium on citric acid fermentation was investigated. We demonstrated that excessive sodium did not increase oxidative stress for Aspergillus niger, but reduced the pH of the medium significantly over the period 4-24 h, which led to lower activities of glucoamylase and isomaltase secreted by A. niger, with a decrease of available sugar concentration and citric acid production. ADE was pretreated by air-stripping prior to recycle and 18 g/L calcium carbonate was added at the start of fermentation to control the pH of the medium. The inhibition caused by ADE was completely alleviated and citric acid production substantially increased from 118.6 g/L to 141.4 g/L, comparable to the fermentation with deionized water (141.2 g/L). This novel process could decrease wastewater discharges and fresh water consumption in the citric acid industry, with benefit to the environment.

The Development of a Sorghum Bran-Based Biorefining Process to Convert Sorghum Bran into Value Added Products.

Sorghum bran, a starch rich food processing waste, was investigated for the production of glucoamylase in submerged fungal fermentation using Aspergillus awamori. The fermentation parameters, such as cultivation time, substrate concentration, pH, temperature, nitrogen source, mineral source and the medium loading ratio were investigated. The glucoamylase activity was improved from 1.90 U/mL in an initial test, to 19.3 U/mL at 10% (w/v) substrate concentration, pH 6.0, medium loading ratio of 200 mL in 500 mL shaking flask, with the addition of 2.5 g/L yeast extract and essential minerals. Fermentation using 2 L bioreactors under the optimum conditions resulted in a glucoamylase activity of 23.5 U/mL at 72 h, while further increase in sorghum bran concentration to 12.5% (w/v) gave an improved gluco-amylase activity of 37.6 U/mL at 115 h. The crude glucoamylase solution was used for the enzymatic hydrolysis of the sorghum bran. A sorghum bran hydrolysis carried out at 200 rpm, 55 °C for 48 h at a substrate loading ratio of 80 g/L resulted in 11.7 g/L glucose, similar to the results obtained using commercial glucoamylase. Large-scale sorghum bran hydrolysis in 2 L bioreactors using crude glucoamylase solution resulted in a glucose concentration of 38.7 g/L from 200 g/L sorghum bran, corresponding to 94.1% of the theoretical hydrolysis yield.

Novel amylase-producing fungus hydrolyzing wheat and brewing residues, Aspergillus carbonarius, discovered in tropical forest remnant.

Today, many microbial amylases are available commercially and they have almost completely replaced chemical hydrolysis in several industry processes. Amylases from microorganisms have a broad spectrum of industrial applications as they are more stable than amylases obtained from plants and animals. The objective of this work was to use potato baits in an Atlantic Forest remnant located in Ribeirão Preto, São Paulo, Brazil, in order to obtain amylase-producing fungi with potential for biotechnological application. In addition, the culture conditions for the fungal strain that presented higher production of glucoamylase were standardized using industrial wastes. For this, 6 PET bottles containing potatoes as baits were scattered at different points in an Atlantic forest remnant. After 6days, the samples were collected, and the filamentous fungi were isolated in Petri dishes. Fungi screening was carried out in Khanna liquid medium with 1% starch Reagen®, at 30°C, pH 6.0, under static conditions for 4days. Proteins and glucoamylase activity were determined by Bradford and 3,5-dinitrosalicylic acid (DNS), respectively. Among all isolated fungi, A. carbonarius showed the highest glucoamylase production. Its best cultivation conditions were observed in Khanna medium, 4days, at 30°C, pH 6.0, under static condition with 0.1% yeast extract and 1% starch Reagen®. Wheat and brewing residues were also used as inducers for large quantities of glucoamylase production. A. carbonarius showed to be a good alternative for the wheat and brewing waste destinations in order to obtain high added value products.

Production and Application of Thermostable Glucoamylase from Thermotolerant Aspergillus fumigatus via Semisolid State Fermentation

A THERMOTOLERANT fungus Aspergillus fumigatus isolated from agriculture soil, Beheira Governorate, Egypt was screened from other fungal isolates for its high glucoamylase activity. The identification of the fungus based on morphology and sequence analysis of ITS1-5.8S rDNA-ITS2. Five crop wastes (wheat bran, wheat straw, rice hulls, rice straw and broken rice grain) were used to induce the thermostable glucoamylase production by A. fumigatus via semisolid state fermentation. Wheat bran is the most suitable waste for glucoamylase production by the tested fungus which further improved using Plackett-Burman and Box-Behnken designs. Optimum conditions for the production of thermostable amylase are reached at pH 6, wheat bran 1gm, yeast extract 6mg/gm, berij 35 40μL/gm, (NH4)2SO4 24mg/gm and an inoculum of 6x 105spore/ml with thermostable glucoamylase production titer of 161.11U/gm after 6 days.FeCl3, BaCl2, and CaCl2 positively affect glucoamylase activity with highest main effect value of FeCl3 ions where MgCl2 has the highest negative main effect on activity. The kinetic constants Km is 1.37mg/ml with three bands in zymogram. Moreover the enzyme showed good cleaning effect when applied in starch patches in textile. Glucoamylase of A. fumigatus exhibited good thermostability as it loss only 28.95% from its original activity after treatment with heat at 80°C for 3hr. Finally, the thermostable glucoamylase from A. fumigatus can be produced from cheap agrowaste via simple fermentation technique.

Polyphasic Characterization of Yeasts and Lactic Acid Bacteria Metabolic Contribution in Semi-Solid Fermentation of Chinese Baijiu (Traditional Fermented Alcoholic Drink): Towards the Design of a Tailored Starter Culture.

Chinese Baijiu is principally produced through a spontaneous fermentation process, which involves complex microorganism communities. Among them, yeasts and lactic acid bacteria (LAB) are important communities. The study examined the isolated strains from fermented grains of Baijiu regarding their activity of α-amylase and glucoamylase, ethanol tolerance, glucose utilization, as well as metabolite production in the process of laboratory-scale sorghum-based fermentation. Selected strains (Saccharomycopsis fibuligera 12, Saccharomyces cerevisiae 3, and Pediococcus acidilactici 4) were blended in different combinations. The influence of selected strains on the metabolic variation in different semi-solid fermentations was investigated by gas chromatography–mass spectrometry (GC–MS) accompanied by multivariate statistical analysis. According to the principal component analysis (PCA), the metabolites produced varied in different mixtures of pure cultures. S. fibuligera produced various enzymes, particularly α-amylase and glucoamylase, and exhibited a better performance compared with other species regarding the ability to convert starch to soluble sugars and positively affect the production process of volatile compounds. S. cerevisiae had a high fermentation capacity, thereby contributing to substrates utilization. Lactic acid bacteria had a good ability to produce lactic acid. This study attaches importance to the special functions of S. fibuligera, S. cerevisiae, and P. acidilactici in Chinese Baijiu making, and investigates their metabolic characteristics in the process of lab-scale semi-solid fermentation.

Digestibility and structures of vinasse starches with different types of raw rice and fermented leaven

In consideration of health benefits, more digestible vinasses were investigated, which are associated with the use of different raw cereals and fermented leavens. In an in vitro digestibility test, milled long-grain glutinous rice vinasse with Taibai rice leaven showed a slow glucose-controlled release potential, which contained 37.08% slowly digestible starch, after complete vinasse consumption. The crystalline structure, thermal properties and morphology of vinasse starches were analysed. The relatively long amylopectin chains, which originated from the starch structure present in raw rice and the higher glucoamylase activity of the fermented leaven, partly explained the slower digestion of vinasse. By the optimization of the type of fermented leaven used and the starch structure of the raw rice in fermentation, the rate of vinasse starch digestion could be controlled, resulting in improved nutritional value. The results of this study are important for designing healthy vinasse products by controlling starch structures and digestion rates.

Overexpression of amyA and glaA substantially increases glucoamylase activity in Aspergillus niger.

The purpose of this study was to obtain an engineered Aspergillus niger strain with high glucoamylase activity by overexpressing the glucoamylase gene glaA and α-amylase gene amyA in A. niger CICC2462. Three recombinant strains containing a single copy of amyA (1A), containing two copies of amyA (2A), and coexpressing amyA and glaA (AG), respectively, were constructed. The transcript levels of amyA in 1A and 2A were increased by 2.95 folds and 3.09 folds, respectively. The levels of amyA and glaA in AG were increased by 1.21 folds and 2.86 folds, but the maximum extracellular glucoamylase activities did not differ significantly. In addition, after 1% casein phosphopeptides (CPPs) was added to the fermentation medium, the maximum extracellular glucoamylase activities for strains 1A, 2A, and AG were 35,200, 37,300, and 40,710 U/ml, respectively, which were significantly higher than that of the parental strain CICC2462 (28,250 U/ml), while CPPs alone had no effect on the parental strain CICC2462. We demonstrate that overexpression of amyA and glaA substantially increases the expression and secretion of glucoamylase in A. niger, and CPPs effectively improves the yield of glucoamylase in recombinant A. niger strains overexpressing amyA and glaA. The newly developed strains and culture methods may have extensive industrial applications.