Production of mannitol from inulin by simultaneous enzymatic saccharification and fermentation with Lactobacillus intermedius NRRL B-3693

Expanding sugar alcohol industry: Microbial production of sugar alcohols and associated chemocatalytic derivatives

Sugar alcohols are polyols that are widely employed in the production of chemicals, pharmaceuticals, and food products. Chemical synthesis of polyols, however, is complex and necessitates the use of hazardous compounds. Therefore, the use of microbes to produce polyols has been proposed as an alternative to traditional synthesis strategies. Many biotechnological approaches have been described to enhancing sugar alcohols production and microbe-mediated sugar alcohol production has the potential to benefit from the availability of inexpensive substrate inputs. Among of them, microbe-mediated erythritol production has been implemented in an industrial scale, but microbial growth and substrate conversion rates are often limited by harsh environmental conditions. In this review, we focused on xylitol, mannitol, sorbitol, and erythritol, the four representative sugar alcohols. The main metabolic engineering strategies, such as regulation of key genes and cofactor balancing, for improving the production of these sugar alcohols were reviewed. The feasible strategies to enhance the stress tolerance of chassis cells, especially thermotolerance, were also summarized. Different low-cost substrates like glycerol, molasses, cellulose hydrolysate, and CO₂ employed for producing these sugar alcohols were presented. Given the value of polyols as precursor platform chemicals that can be leveraged to produce a diverse array of chemical products, we not only discuss the challenges encountered in the above parts, but also envisioned the development of their derivatives for broadening the application of sugar alcohols.

Mannitol Production by Heterofermentative Lactic Acid Bacteria: a Review

Obesity, diabetes, and other cardiovascular diseases are directly related to the high consumption of processed sugars with high caloric content. The current food industry has novel trends related to replacing highly caloric sugars with non-caloric or low-calorie sweeteners. Mannitol, a polyol, represents a suitable substitute because it has a low caloric content and does not induce a glycemic response, which is crucial for diabetic people. Consequently, this polyol has multiple applications in the food, pharmaceutical, and medicine industries. Mannitol can be produced by plant extraction, chemical or enzymatic synthesis, or microbial fermentation. Different in vitro processes have been developed regarding enzymatic synthesis to obtain mannitol from fructose, glucose, or starch-derived substrates. Various microorganisms such as yeast, fungi, and bacteria are applied for microbial fermentation. Among them, heterofermentative lactic acid bacteria (LAB) represent a reliable and feasible alternative due to their metabolic characteristics. In this regard, the yield and productivity of mannitol depend on the culture system, the growing conditions, and the culture medium composition. In situ mannitol production represents a novel approach to decrease the sugar content in food and beverages. Also, genetic engineering offers an interesting option to obtain mannitol-producing strains. This review presents and discusses the most significant advances that have been made in the mannitol production through fermentation by heterofermentative LAB, including the pertinent and critical analysis of culture conditions considering broth composition, reaction systems, and their effects on productivities and yields.

Evaluation of lactic acid bacteria strains isolated from fructose-rich environments for their mannitol-production and milk-gelation abilities

Mannitol is a sugar alcohol, or polyol, widely used in the food industry because of its low-calorie properties. Industrial production of mannitol is difficult and expensive. However, certain bacterial species are known to produce mannitol naturally, including certain lactic acid bacteria and fructophilic lactic acid bacteria (LAB). In this study, bacterial strains isolated from fructose-rich sources, including flowers, leaves, and honey, were identified by 16S rRNA sequence analysis as Leuconostoc, Fructobacillus, Lactococcus, and Lactobacillus species and 4 non-LAB species. DNA profiles generated by pulsed-field gel electrophoresis discriminated 32 strains of Leuconostoc mesenteroides and 6 Fructobacillus strains. Out of 41 LAB strains isolated, 32 were shown to harbor the mdh gene, which encodes the mannitol dehydrogenase enzyme, and several showed remarkable fructose tolerance even at 50% fructose concentrations, indicating their fructophilic nature. Several of the strains isolated, including Leuconostoc mesenteroides strains DPC 7232 and DPC 7261, Fructobacillus fructosus DPC 7237, and Fructobacillus fructosus DPC 7238, produced higher mannitol concentrations than did the positive control strain Limosilactobacillus reuteri DSM 20016 during an enzymatic screening assay. Mannitol concentrations were also examined via HPLC in 1% fructose de Man, Rogosa, and Sharpe medium (FMRS) or 1% fructose milk (FM). Among the strains, Fructobacillus fructosus DPC 7238 displayed high fructose utilization (9.27 g/L), high mannitol yield (0.99 g of mannitol/g of fructose), and greatest volumetric productivities (0.46 g/L per h) in FMRS. However, Leuconostoc mesenteroides DPC 7261 demonstrated the highest fructose utilization (8.99 g/L), mannitol yield (0.72 g of mannitol/g of fructose), and volumetric productivities (0.04 g/L per h) in FM. Storage modulus G' (>0.1 Pa) indicated a shorter gelation time for Limosilactobacillus reuteri DSM 20016 (8.73 h), followed by F. fructosus DPC 7238 (11.57 h) and L. mesenteroides DPC 7261 (14.52 h). Our results show that fructose-rich niches can be considered important sources of fructophilic LAB strains, with the potential to be used as starter cultures or adjunct cultures for the manufacture of mannitol-enriched fermented dairy products and beverages.

Enhanced production of Aspergillus niger inulinase from sugar beet molasses and its kinetic modeling

OBJECTIVE

The fermentation medium contains many complex components (vitamins, minerals, etc.) for better growth of the microorganisms. The increasing purity and number of these components used in the medium seriously affect the cost of the microbial process. This study aimed to further optimize the concentration of the components used in the medium (yeast extract and peptone) for inulinase fabrication by Aspergillus niger from sugar-beet molasses in shake flask fermentation by using Central Composite Design (CCD) and to kinetically identify the fermentation.

RESULTS

The results indicated that the optimal medium composition consisted of only 4.2% (w/v) yeast extract. By using the fermentation environment, the inulinase generation, inulinase/sucrase ratio, maximum inulinase generation rate, maximum sugar depletion rate, and substrate utilization yield were determined as 1294.5 U/mL, 1.2, 159.6 U/mL/day, 7.4 g/L/day, and 98.1%, respectively. The kinetic analysis of the fungal development (logistic model) indicated that a specific development rate and initial biomass concentration were 0.89/day and 1.79 g/L, respectively. Inulinase and sucrase productions are mixed-development associated since the α value ≠ 0 (8.46 and 4.31 U/mgX) and the β value ≠ 0 (5.15 and 4.83 U/mgX day), respectively (Luedeking-Piret model). Besides, the maintenance value (Z) (0.009 gS/gX day) was lower than γ value (1.044 gS/gX), showing that A. niger commonly uses the substrates for enzyme fabrication and fungal development (modified Luedeking-Piret model).

CONCLUSIONS

The enzyme activity was increased by optimizing the concentration of the components used. It was demonstrated that the proposed kinetic models can victoriously define fungal development, enzyme fabrication, and sugar depletion.

Recent advances in the biotechnological production of erythritol and mannitol

Dietary habits that include an excess of added sugars have been strongly associated with an increased risk of obesity, heart disease, diabetes, and tooth decay. With this association in view, modern food systems aim to replace added sugars with low calorie sweeteners, such as polyols. Polyols are generally not carcinogenic and do not trigger a glycemic response. Furthermore, owing to the absence of the carbonyl group, they are more stable compared to monosaccharides and do not participate in Maillard reactions. As such, since polyols are stable at high temperatures, and they do not brown or caramelize when heated. Therefore, polyols are widely used in the diets of hypocaloric and diabetic patients, as well as other specific cases where controlled caloric intake is required. In recent years, erythritol and mannitol have gained increased importance, especially in the food and pharmaceutical industries. In these areas, research efforts have been made to improve the productivity and yield of the two polyols, relying on biotechnological manufacturing methods. The present review highlights the recent advances in the biotechnological production of erythritol and mannitol and summarizes the benefits of using the two polyols in the food and pharmaceutical industries.

A review of polyols - biotechnological production, food applications, regulation, labeling and health effects

Food research is constantly searching for new ways to replace sugar. This is due to the negative connotations of sugar consumption on health which has driven consumer demand for healthier products and is reflected on a national level by the taxation of sugary beverages. Sugar alcohols, a class of polyols, are present in varying levels in many fruits and vegetables and are also added to foods as low calorific sweeteners. The most commonly used polyols in food include sorbitol, mannitol, xylitol, erythritol, maltitol, lactitol and isomalt. Of these, microorganisms can produce sorbitol, mannitol, xylitol and erythritol either naturally or through genetic engineering. Production of polyols by microbes has been the focus of a lot of research for its potential as an alternative to current industrial scale production by chemical synthesis but can also be used for in situ production of natural sweeteners in fermented products using microbes approved for use in foods. This review on the generation of these natural sweetening compounds by microorganisms examines the current understanding and methods of microbial production of polyols that are applicable in the food industry. The review also considers the health benefits and effects of polyol usage and discusses regulations which are applicable to polyol use.

Diversity and Functional Properties of Lactic Acid Bacteria Isolated From Wild Fruits and Flowers Present in Northern Argentina

Lactic acid bacteria (LAB) are capable of converting carbohydrate substrates into organic acids (mainly lactic acid) and producing a wide range of metabolites. Due to their interesting beneficial properties, LAB are widely used as starter cultures, as probiotics, and as microbial cell factories. Exploring LAB present in unknown niches may lead to the isolation of unique species or strains with relevant technological properties. Autochthonous rather than allochthonous starter cultures are preferred in the current industry of fermented food products, due to better adaptation and performance of autochthonous strains to the matrix they originate from. In this work, the lactic microbiota of eight different wild tropical types of fruits and four types of flowers were studied. The ability of the isolated strains to produce metabolites of interest to the food industry was evaluated. The presence of 21 species belonging to the genera Enterococcus, Fructobacillus, Lactobacillus, Lactococcus, Leuconostoc, and Weissella was evidenced by using culture-dependent techniques. The isolated LAB corresponded to 95 genotypically differentiated strains by applying rep-PCR and sequencing of the 16S rRNA gene; subsequently, representative strains of the different isolated species were studied for technological properties, such as fast growth rate and acidifying capacity; pectinolytic and cinnamoyl esterase activities, and absence of biogenic amine biosynthesis. Additionally, the strains' capacity to produce ethyl esters as well as mannitol was evaluated. The isolated fruit- and flower-origin LAB displayed functional properties that validate their potential use in the manufacture of fermented fruit-based products setting the background for the design of novel functional foods.

Biotechnological applications of inulin-rich feedstocks

Inulin is a naturally occurring second largest storage polysaccharide with a wide range of applications in pharmaceutical and food industries. It is a robust polysaccharide which consists of a linear chain of β-2, 1-linked-d-fructofuranose molecules terminated with α-d-glucose moiety at the reducing end. It is present in tubers, bulbs and tuberous roots of more than 36,000 plants belonging to both monocotyledonous and dicotyledonous families. Jerusalem artichoke, chicory, dahlia, asparagus, etc. are important inulin-rich plants. Inulin is a potent substrate and inducer for the production of inulinases. Inulin/inulin-rich feedstocks can be used for the production of fructooligosaccharides and high-fructose syrup. Additionally, inulin-rich feedstocks can also be exploited for the production of other industrially important products like acetone, butanol, bioethanol, single cell proteins, single cell oils, 2, 3-butanediol, sorbitol, mannitol, etc. Current review highlights the biotechnological potential of inulin-rich feedstocks for the production of various industrially important products.

Recent advances in microbial production of mannitol: utilization of low-cost substrates, strain development and regulation strategies

Mannitol has been widely used in fine chemicals, pharmaceutical industries, as well as functional foods due to its excellent characteristics, such as antioxidant protecting, regulation of osmotic pressure and non-metabolizable feature. Mannitol can be naturally produced by microorganisms. Compared with chemical manufacturing, microbial production of mannitol provides high yield and convenience in products separation; however the fermentative process has not been widely adopted yet. A major obstacle to microbial production of mannitol under industrial-scale lies in the low economical efficiency, owing to the high cost of fermentation medium, leakage of fructose, low mannitol productivity. In this review, recent advances in improving the economical efficiency of microbial production of mannitol were reviewed, including utilization of low-cost substrates, strain development for high mannitol yield and process regulation strategies for high productivity.

Microbial production of mannitol by Lactobacillus brevis 3-A5 from concentrated extract of Jerusalem artichoke tubers

In the present study, the conversion of the extract of Jerusalem artichoke tubers for mannitol production by Lactobacillus brevis 3-A5 was investigated. When the bacterium utilized enzymatic hydrolysates of Jerusalem artichoke extract as the main substrates in batch fermentation, the significant decrease in mannitol productivity was observed when the initial concentration of reducing sugar increased. Then, a strategy of continuous fed-batch fermentation was adopted for improving mannitol production with enzymatic hydrolysates of Jerusalem artichoke extract as main substrates. Although the concentration of mannitol could reach 199.86 g/L at the end of the fermentation, the productivity for the overall process of the fermentation was only 1.67 g/L/H. To improve the mannitol productivity with both higher yield and concentration, the simultaneous enzymatic saccharification and fermentation (SSF) was studied. In SSF, the mannitol production reached 176.50 g/L in 28 H with a productivity of 6.30 g/L/H and a yield of 0.68 g/g total sugar. Our study provides a cost-effective and eco-friendly method for mannitol production from a cheap biomass.

High-yield production of mannitol by Leuconostoc pseudomesenteroides CTCC G123 from chicory-derived inulin hydrolysate

Chicory is an agricultural plant with considerable potential as a carbohydrate substrate for low-cost production of biochemicals. In this work, the production of mannitol by Leuconostoc pseudomesenteroides CTCC G123 from chicory-derived inulin hydrolysate was investigated. The bioconversion process initially suffered from the leakage of fructose to the phosphoketolase pathway, resulting in a low mannitol yield. When inulin hydrolysate was supplemented with glucose as a substrate for mannitol production in combination with aeration induction and nicotinic acid induced redox modulation strategies, the mannitol yield greatly improved. Under these conditions, significant improvement in the glucose consumption rate, intracellular NADH levels and mannitol dehydrogenase specific activity were observed, with mannitol production increasing from 64.6 to 88.1 g/L and overall yield increase from 0.69 to 0.94 g/g. This work demonstrated an efficient method for the production of mannitol from inulin hydrolysate with a high overall yield.

A panorama of bacterial inulinases: Production, purification, characterization and industrial applications

Inulinases are important hydrolysing enzymes which specifically act on β-2, 1 linkages of inulin to produce fructose or fructooligosaccharides. Fungi, yeasts and bacteria are the potent microbial sources of inulinases. The data on bacterial inulinases is scarce as compared to other microbial sources. Inulinases yield from bacteria is very less as compared to fungal and yeast sources of inulinases. Submerged fermentation (SmF) is the method of choice for the production of inulinases from bacterial sources. Moreover, inulin is a potent substrate for the production of inulinases in SmF. Many bacterial inulinases have been reported to display magnificent environment abiding features and variability in their biophysical and biochemical properties. These properties have attracted intention of many researchers towards exploring adverse ecological niches for more distinctive inulinase producing bacterial strains. Inulinases are substantially important in current biotechnological era due to their numerous industrial applications. High fructose syrup and fructooligosaccharides are two major industrial applications of inulinases. Additionally, there are many reports on the production of various metabolites like citric acid, lactic acid, ethanol, biofuels, butanediol etc. using mixed cultures of inulinase producing organisms with other microorganisms. The present review mainly envisages inulinase producing bacterial sources, inulinase production, purification, characterization and their applications.

Biotechnological and in situ food production of polyols by lactic acid bacteria

Polyols such as mannitol, erythritol, sorbitol, and xylitol are naturally found in fruits and vegetables and are produced by certain bacteria, fungi, yeasts, and algae. These sugar alcohols are widely used in food and pharmaceutical industries and in medicine because of their interesting physicochemical properties. In the food industry, polyols are employed as natural sweeteners applicable in light and diabetic food products. In the last decade, biotechnological production of polyols by lactic acid bacteria (LAB) has been investigated as an alternative to their current industrial production. While heterofermentative LAB may naturally produce mannitol and erythritol under certain culture conditions, sorbitol and xylitol have been only synthesized through metabolic engineering processes. This review deals with the spontaneous formation of mannitol and erythritol in fermented foods and their biotechnological production by heterofermentative LAB and briefly presented the metabolic engineering processes applied for polyol formation.

Application of low magnetic field on inulinase production by Geotrichum candidum under solid state fermentation using leek as substrate

This study evaluates the application of low magnetic field (LMF) on inulinase enzyme production by Geotrichum candidum under solid state fermentation (SSF) using leek as potential carbon source. First, the fermentation conditions were optimized using normal magnetic field grown microorganism. Among eight G. candidum isolates, the most effective strain called G. candidum OC-7 was selected to use in further experiments. In the second part of the study, SSF was carried out under different LMFs (4 and 7 mT). The results showed that inulinase activity was strongly affected by LMF application. The highest enzyme activity was obtained as 535.2 U/g of dry substrate (gds) by 7 mT magnetic field grown G. candidum OC-7. On the contrary, the control had only 412.1 U/gds. Consequently, the use of leek presents a great potential as an alternative carbon source for inulinase production and magnetic field treatment could effectively be used in order to enhance the enzyme production.

Sensorically and antimicrobially active metabolite production of Lactobacillus strains on Jerusalem artichoke juice

BACKGROUND

In the tubers of Jerusalem artichoke (Helianthus tuberosus L.) the main carbohydrate is the well-known prebiotic inulin, which is a good growth substrate for gut microorganisms. Jerusalem artichoke tuber is traditionally consumed boiled or pickled rather than in fermented form. Lactic acid bacteria are traditionally used in the production of fermented foods; nevertheless their behavior and metabolite production are considerably influenced by the substrate. The purpose of this study was to investigate the growth and production of the most important sensorically and antimicrobially active metabolites of different Lactobacillus strains on Jerusalem artichoke juice.

RESULTS

All investigated strains grew well (in the range 10(9) cfu mL(-1) ) in the media. The organic acids (lactic acid, 110-337 mmol L(-1) ; acetic acid, 0-180 mmol L(-1) ; and succinic acid, 0-79 mmol L(-1) ), hydrogen peroxide (0.25-1.77 mg L(-1) ), mannitol (0.06-3.24 g L(-1) ), acetoin and diacetyl production of strains varies not only according to the species but also from strain to strain, which will be demonstrated and discussed in the paper.

CONCLUSION

Our results showed that lactobacilli can be used for the fermentation of Jerusalem artichoke, which in this form could be used, alone or mixed with other raw food material, as a new synbiotic functional food.

Biotechnological potential of inulin for bioprocesses

Inulin consists of linear chains of β-2,1-linked D-fructofuranose molecules terminated by a glucose residue through a sucrose-type linkage at the reducing end. In this review article, inulin and its applications in bioprocesses are overviewed. The tubers of many plants, such as Jerusalem artichoke, chicory, dahlia, and yacon contain a large amount of inulin. Inulin can be actively hydrolyzed by microbial inulinases to produce fructose, glucose and inulooligosaccharides (IOS). The fructose and glucose formed can be further transformed into ethanol, single-cell protein, single cell oil and other useful products by different microorganisms. IOS formed have many functions. Therefore, inulin can be widely used in food, feed, pharmaceutical, chemical and biofuels industries.

Biotechnological production of mannitol and its applications

Mannitol, a naturally occurring polyol (sugar alcohol), is widely used in the food, pharmaceutical, medical, and chemical industries. The production of mannitol by fermentation has become attractive because of the problems associated with its production chemically. A number of homo- and heterofermentative lactic acid bacteria (LAB), yeasts, and filamentous fungi are known to produce mannitol. In particular, several heterofermentative LAB are excellent producers of mannitol from fructose. These bacteria convert fructose to mannitol with 100% yields from a mixture of glucose and fructose (1:2). Glucose is converted to lactic acid and acetic acid, and fructose is converted to mannitol. The enzyme responsible for conversion of fructose to mannitol is NADPH- or NADH-dependent mannitol dehydrogenase (MDH). Fructose can also be converted to mannitol by using MDH in the presence of the cofactor NADPH or NADH. A two enzyme system can be used for cofactor regeneration with simultaneous conversion of two substrates into two products. Mannitol at 180 g l(-1) can be crystallized out from the fermentation broth by cooling crystallization. This paper reviews progress to date in the production of mannitol by fermentation and using enzyme technology, downstream processing, and applications of mannitol.

Quantitative characterization of nonstructural carbohydrates of mezcal Agave (Agave salmiana Otto ex Salm-Dick)

Fructans are the reserve carbohydrates in Agave spp. plants. In mezcal factories, fructans undergoes thermal hydrolysis to release fructose and glucose, which are the basis to produce this spirit. Carbohydrate content determines the yield of the final product, which depends on plant organ, ripeness stage, and thermal hydrolysis. Thus, a qualitative and quantitative characterization of nonstructural carbohydrates was conducted in raw and hydrolyzed juices extracted from Agave salmiana stems and leaves under three ripeness stages. By high-performance liquid chromatography (HPLC), fructose, glucose, sucrose, xylose, and maltose were identified in agave juice. Only the plant fraction with hydrolysis interaction was found to be significant in the glucose concentration plant. Interactions of the fraction with hydrolysis and ripeness with hydrolysis were statistically significant in fructose concentration. Fructose concentration rose considerably with hydrolysis, but only in juice extracted from ripe agave stems (early mature and castrated). This increase was statistically significant only with acid hydrolysis.