Effect of Several Pretreatments on the Lactic Acid Production from Exhausted Sugar Beet Pulp.

Exhausted sugar beet pulp (ESBP), a by-product of the sugar industry, has been used as a substrate to produce lactic acid (LA). Due to the fact that ESBP contains a high percentage of pectin and hemicellulose, different pretreatments were studied to solubilize them and to facilitate the access to cellulose in the subsequent enzymatic hydrolysis. Several pretreatments were studied, specifically biological, oxidant with alkaline hydrogen peroxide (AHP), and thermochemical with acid (0.25, 0.5, or 1% w/v of H2SO4). Pretreated ESBP was enzymatically hydrolysed and fermented with the strain Lactiplantibacillus plantarum for LA production. The hydrolysis was carried out with the commercial enzymes Celluclast®, pectinase, and xylanase, for 48 h. After that, the hydrolysate was supplemented with yeast extract and calcium carbonate before the bacteria inoculation. Results showed that all the pretreatments caused a modification of the fibre composition of ESBP. In most cases, the cellulose content increased, rising from 25% to 68% when ESBP was pretreated thermochemically at 1% w/v H2SO4. The production of LA was enhanced when ESBP was pretreated thermochemically. However, it was reduced when biological and AHP pretreatments were applied. In conclusion, thermochemical pretreatment with 1% w/v H2SO4 had a positive impact on the production of LA, increasing its concentration from 27 g/L to 50 g/L.

Valorisation of fungal hydrolysates of exhausted sugar beet pulp for lactic acid production.

BACKGROUND: Exhausted sugar beet pulp pellets (ESBPP) were used as raw material for lactic acid (LA) fermentation. The enzymatic hydrolysis of ESBPP was performed with the solid obtained after the fungal solid-state fermentation of ESBPP as a source of hydrolytic enzymes. Subsequently, a medium rich in glucose and arabinose was obtained, which was used to produce LA by fermentation. For LA production, two Lactobacillus strains were assayed and the effects of the supplementation of the hydrolysate with a nitrogen source and the mode of pH regulation of the fermentation were investigated. Moreover, a kinetic model for LA fermentation by Lactobacillus plantarum of ESBPP hydrolysates was developed. RESULTS: L. plantarum produced a LA concentration 34% higher than that produced by L. casei. The highest LA concentration (30 g L-1 ) was obtained with L. plantarum when the hydrolysate was supplemented with 5 g L-1 yeast extract and the pH was controlled with CaCO3 . The concentration of acetic acid differed depending on the concentration of CaCO3 added, producing its maximum value with 27 g L-1 CaCO3 . The proposed kinetic model was able to predict the evolution of substrates and products depending on the variation of the pH in the hydrolysate, according to the amount of CaCO3 added. CONCLUSIONS: ESBPP can be revalorised to produce LA. A pure LA stream or a mixture of LA and acetic acid, depending on the pH control method of the fermentation, can be produced. Thus, this control is of great interest depending on the destination of the effluent. © 2020 Society of Chemical Industry.

Conversion of Exhausted Sugar Beet Pulp into Fermentable Sugars from a Biorefinery Approach.

In this study, the production of a hydrolysate rich in fermentable sugars, which could be used as a generic microbial culture medium, was carried out by using exhausted sugar beet pulp pellets (ESBPPs) as raw material. For this purpose, the hydrolysis was performed through the direct addition of the fermented ESBPPs obtained by fungal solid-state fermentation (SSF) as an enzyme source. By directly using this fermented solid, the stages for enzyme extraction and purification were avoided. The effects of temperature, fermented to fresh solid ratio, supplementation of fermented ESBPP with commercial cellulase, and the use of high-solid fed-batch enzymatic hydrolysis were studied to obtain the maximum reducing sugar (RS) concentration and productivity. The highest RS concentration and productivity, 127.3 g·L-1 and 24.3 g·L-1·h-1 respectively, were obtained at 50 °C and with an initial supplementation of 2.17 U of Celluclast® per gram of dried solid in fed-batch mode. This process was carried out with a liquid to solid ratio of 4.3 mL·g-1 solid, by adding 15 g of fermented solid and 13.75 g of fresh solid at the beginning of the hydrolysis, and then the same amount of fresh solid 3 times every 2.5 h. By this procedure, ESBPP can be used to produce a generic microbial feedstock, which contains a high concentration of monosaccharides.

Feasibility of exhausted sugar beet pulp as raw material for lactic acid production.

BACKGROUND: Exhausted sugar beet pulp pellets (ESBPP), a sugar industry by-product generated after sugar extraction in the sugar production process, have been used as a raw material for lactic acid (LA) production via hydrolysis and fermentation by Lactobacillus casei. To design a more cost-effective process, simultaneous saccharification and fermentation (SSF) of ESBPP is proposed in the present study. The effects of pH control, nutrient supplementation and solid addition in fed-batch SSF on lactic acid production were investigated. RESULTS: The highest LA concentration (26.88 g L-1 ) was reached in fed-batch SSF at a solid/liquid loading of 0.2 g mL-1 , with pH control (by adding 30 g L-1 CaCO3 to the medium) and nutrient supplementation (by adding 20 mL of MRS medium per 100 mL of buffer). Under these conditions, a maximum productivity of 0.63 g L-1 h-1 was achieved, which is 2.7 times higher than that attained in the control experiment (SSF inoculated at time 0 h). However, a slightly lower LA yield was obtained, revealing the need of an increasing dose of enzymes at high solid loading SSF. CONCLUSION: An efficient fed-batch SSF strategy with pH control and MRS supplementation is described in the present study, attaining higher LA productivity compared to separate hydrolysis and fermentation and SSF. © 2020 Society of Chemical Industry.

Orange peels: from by-product to resource through lactic acid fermentation.

BACKGROUND: Considering the large amounts of by-products derived from orange processing, which are generally discarded, the present study aimed to explore the feasibility of using orange peel for lactic acid production in solid state fermentation. RESULTS: Different species of lactic acid bacteria were employed, singly and in co-culture, to evaluate their ability to ferment orange peel and produce lactic acid. Among the single cultures tested, Lactobacillus casei 2246 was the most efficient strain, reaching the highest concentration of lactic acid (209.65 g kg-1 ) and yield (0.88 g g-1 ). The use of Lactobacillus plantarum 285 and Lactobacillus paracasei 4186 in co-culture produced a comparable amount of lactic acid, showing a better performance than the same strains in single cultures. CONCLUSION: Orange peels represent a suitable raw material for solid state fermentation employing lactic acid bacteria. Lactic acid was obtained that consumed the most of sugars available, leading to high yields. Despite all the strains tested showing the same growth ability, different peculiarities in lactic acid production were revealed, dependent on the species/strains, suggesting the relevance of strain selection. © 2019 Society of Chemical Industry.

Effect on White Grape Must of Multiflora Bee Pollen Addition during the Alcoholic Fermentation Process.

The aim of the present study was to compare and analyze the impact of using bee pollen doses (0.1, 0.25, 1, 5, 10 and 20 g/L) as activator in the alcoholic fermentation process of Palomino fino and Riesling wines. In this regard, its influence on the musts composition, the fermentative kinetics, the evolution of the populations of Saccharomyces cerevisiae, the evolution of yeast-assimilable nitrogen and physico-chemical characteristics of final wines has been analyzed. Bee pollen addition produces significant increases in yeast-assimilable nitrogen and maximum yeasts population and exponential velocity reached during alcoholic fermentation. Bee pollen showed an important effect on yeast survival during the death phase. Final wines showed significantly increase in volatile acidity above doses higher than 10 g/L and Comisión Internacional de L'Eclairage parameters (CIELab), color intensity and Abs 420 nm, from 1 g/L. Therefore, pollen could be used as fermentative activator for the alcoholic fermentation of white wines applying doses below of 1 g/L.

Modelling of different enzyme productions by solid-state fermentation on several agro-industrial residues.

A simple kinetic model, with only three fitting parameters, for several enzyme productions in Petri dishes by solid-state fermentation is proposed in this paper, which may be a valuable tool for simulation of this type of processes. Basically, the model is able to predict temporal fungal enzyme production by solid-state fermentation on complex substrates, maximum enzyme activity expected and time at which these maxima are reached. In this work, several fermentations in solid state were performed in Petri dishes, using four filamentous fungi grown on different agro-industrial residues, measuring xylanase, exo-polygalacturonase, cellulose and laccase activities over time. Regression coefficients after fitting experimental data to the proposed model turned out to be quite high in all cases. In fact, these results are very interesting considering, on the one hand, the simplicity of the model and, on the other hand, that enzyme activities correspond to different enzymes, produced by different fungi on different substrates.

Comparison of industrially viable pretreatments to enhance soybean straw biodegradability.

This study explores acid and alkaline pretreatments in order to enhance soybean straw biodegradability. The effects of sulfuric acid and sodium hydroxide for different pretreatment times at 30°C and 121°C on biomass dissolution and the subsequent enzymatic hydrolysis were investigated. The highest total conversion to reducing sugars of 93.9% was attained when soybean straw was pretreated with acid (4% H2SO4, 121°C, 1 h) and subsequently subjected to the enzymatic process. However, conversion of 86.5%, were reached only with the hydrolysis of the pretreated residue using mild conditions, (0.5% NaOH, 30°C, 48 h), involving the reduction cost of the process. In addition to this, this result was dramatically decreased when pectinase was removed from the enzyme cocktail. It has been also demonstrated that the reduction of the enzyme loading to less than half allowed obtaining about 96% of the reducing sugars attained with the highest enzyme dose.

Alkaline and alkaline peroxide pretreatments at mild temperature to enhance enzymatic hydrolysis of rice hulls and straw.

The current study explores alkaline and alkaline peroxide pretreatments in order to achieve a method to improve saccharification of agricultural residues for ethanol production. The effects of reagent concentration and pretreatment time at 30°C and atmospheric pressure on biomass dissolution after the pretreatment and enzymatic hydrolysis of the pretreated biomass were investigated. In fact, although all pretreatments tested improved enzymatic hydrolysis of native residues, the best results were not achieved for the highest biomass loss. The maximum conversions to reducing sugars in the hydrolysis stage of 77.5% and 92.6% were obtained for rice hulls and straw pretreated by alkaline peroxide (4%, 24h) and alkaline (1%, 48 h) methods, respectively. For both pretreated residues, the reduction to more than half the recommended enzyme loading allowed obtaining more than 94% the reducing sugars attained with the recommended dose.

The influence of ripeness grade on the composition of musts and wines from Vitis vinifera cv. Tempranillo grown in a warm climate.

Fruit ripeness has an influence on the phenolic and aromatic composition of grapes and musts and, therefore, on the sensorial characteristics of the resulting wine. The aim of the work described here was to assess the influence of the harvest date on the analytical composition of the musts and wines from the Vitis vinifera cv. Tempranillo grape grown in a warm climate. A hydroalcoholic medium was employed to extract the musts and simulate a traditional maceration process. Phenolic compounds were analysed by colorimetric methods and aroma compounds by gas chromatography/mass-spectrometry. Furthermore, the wines were tested by a sensory panel. A good correlation was obtained between the parameters measured in the must and in the corresponding wine, as well as in the scores recorded in the sensory analysis. In summary, grape ripening was found to have a marked influence on the wine composition and it was possible to establish the key parameters that need to be measured in the must during ripening to identify the optimal harvest date to obtain the best quality wine.

The influence of cation exchange treatment on the final characteristics of red wines.

Ion exchange technology has been applied to adjust the pH of red wine and improve its tartaric and oxidative stability. Ion exchange appears to be a useful technique to achieve these objectives. Regarding the effect of ion exchange on organoleptic characteristics and the quality of the obtained wines, a slight decrease in both anthocyanin and tannin contents was observed along with a small drop in the aromatic content. However, the treated wines had lower hue and higher colour intensity and gave better punctuations in the sensory evaluation. These results confirm that ion exchange is an interesting technique for application in red winemaking.

Effect of lysozyme on "flor" velum yeasts in the biological aging of sherry wines.

Biological aging is a key step in the production of Sherry wine classified as "fine". During this stage, a film of yeast referred to as "flor velum" covers the surface of the wine and substantially alters its characteristics. Other microorganisms may coexist with flor yeasts, such as lactic acid bacteria and non-Saccharomyces yeasts, whose growth may be favored under certain conditions, causing organoleptic deviations and deterioration of the wine. To prevent the development of lactic bacteria, lysozyme usage has been introduced. Lysozyme is a hydrolytic enzyme with muramidase activity that can lyse gram-positive bacteria; its use in winemaking was approved by the OIV in 1997 (resolution OENO 10/97). Thus far, the use of lysozyme during the production of Sherry wines is not widespread despite its effectiveness in controlling lactic acid bacteria. However, there have been no studies on the effect of lysozyme on flor velum. The aim of this study was to determine the influence of lysozyme on yeast growth and the formation, development and metabolism of flor velum during the biological aging process of Sherry wine. The results indicate that lysozyme does not affect the flor yeast during the fermentative stage or biofilm stage. However, if yeast inoculation is carried out under submerged culture conditions during biological aging, low doses of lysozyme (≥12.5 g/hL) affect cell multiplication and the membrane hydrophobicity of the yeast, inhibiting their aggregation and flotation and the subsequent development of flor velum. Thus, the yeast inoculation protocol and the methodology used for the addition of lysozyme influence velum development, its metabolism and the wine characteristics.

Xylanase production by Aspergillus awamori under solid state fermentation conditions on tomato pomace

In this work, tomato pomace, a waste abundantly available in the Mediterranean and other temperate climates agro-food industries, has been used as raw material for the production of some hydrolytic enzymes, including xylanase, exo-polygalacturonase (exo-PG), cellulase (CMCase) and ¥á-amylase. The principal step of the process is the solid state fermentation (SSF) of this residue by Aspergillus awamori. In several laboratory experiments, maximum xylanase and exo-PG activities were measured during the first days of culture, reaching values around 100 and 80 IU/gds (international units of enzyme activity per gram of dried solid), respectively. For CMCase and ¥á-amylase production remained almost constant along fermentation, with average values of 19 and 21.5 IU/gds, respectively. Experiments carried out in a plate-type bioreactor at lab scale showed a clear positive effect of aeration on xylanase and CMCase, while the opposite was observed for exo-PG and ¥á-amylase. In general, xylanase was the enzyme produced in higher levels, thus the optimum conditions for the determination of the enzyme activity was characterized. The xylanase activity shows an optimum pH of 5 and an optimum temperature of 50 ¨¬C. The enzyme is activated by Mg2+, but strongly inhibited by Hg2+ and Cu2+. The enzymatic activity remains quite high if the extract is preserved in a range of pH from 3 to 10 and a temperature between 30 ¨¬C to 40 ¨¬C.

Xylanase production by Aspergillus awamori under solid state fermentation conditions on tomato pomace.

In this work, tomato pomace, a waste abundantly available in the Mediterranean and other temperate climates agro-food industries, has been used as raw material for the production of some hydrolytic enzymes, including xylanase, exo-polygalacturonase (exo-PG), cellulase (CMCase) and α-amylase. The principal step of the process is the solid state fermentation (SSF) of this residue by Aspergillus awamori. In several laboratory experiments, maximum xylanase and exo-PG activities were measured during the first days of culture, reaching values around 100 and 80 IU/gds (international units of enzyme activity per gram of dried solid), respectively. For CMCase and α-amylase production remained almost constant along fermentation, with average values of 19 and 21.5 IU/gds, respectively. Experiments carried out in a plate-type bioreactor at lab scale showed a clear positive effect of aeration on xylanase and CMCase, while the opposite was observed for exo-PG and α-amylase. In general, xylanase was the enzyme produced in higher levels, thus the optimum conditions for the determination of the enzyme activity was characterized. The xylanase activity shows an optimum pH of 5 and an optimum temperature of 50 ºC. The enzyme is activated by Mg(2+), but strongly inhibited by Hg(2+) and Cu(2+). The enzymatic activity remains quite high if the extract is preserved in a range of pH from 3 to 10 and a temperature between 30 ºC to 40 ºC.

Evolution of resveratrol and piceid contents during the industrial winemaking process of sherry wine.

In the Jerez region, the sherry winemaking process involves a stage of aging carried out in a dynamic system known as "soleras" and "criaderas". In the case of fino sherry, this aging takes place in the presence of a yeast film growing on the surface of the wine, which gives it a very specific character. In this work, the influence of the sherry elaboration process on resveratrol and piceid levels has been studied. With this purpose, the contents of resveratrol isomers and piceid during the main stages of the sherry wine production system, from maturation until bottling, were monitored during two vintages. The results showed that resveratrol contents of both the skin and juice, for Palomino fino grape, are very similar to those described for other white grape varieties. Sherry wine fermentation, clarification, cold stabilization, and filtration processes considerably affect resveratrol and piceid contents. However, biological aging has the most important influence, diminishing their contents by 80%. These results were confirmed in several tests performed in the laboratory, in which various factors that could affect the resveratrol contents during aging were taken into account (oxidative phenomena and a combination with acetaldehyde and "flor" biofilm growth).

Study of the lipidic and proteic composition of an industrial filmogenic yeast with applications as a nutritional supplement.

The lipid and protein contents of yeast strains that form "flor velum" during the aging of sherry wines have been studied during their fermentation and "velum" phases. The same analyses were carried out on two other strains that do not form velum (fermentative strains). The results show a high lipid content in velum yeast during its two phases. This strain changes its lipidic components while passing from the fermentative to the velum phase, with palmitic, palmitoleic, and stearic acid concentrations decreasing, while the oleic, behenic, and lignoceric acid concentrations increase. Furthermore, a higher proteic content can be seen during the filmogenic stage of velum yeast as compared to the fermentative stage of this strain. A well-balanced distribution of amino acids is observed, which includes all essential amino acids. The sulfurated amino acids are shown to be the most limited, and a high quantity of lysine has been detected. Finally, the values of PDCAAS (Protein Digestibility Corrected Amino Acid Score) and MEAA (Modified Index of Essential Amino Acids) of this strain make it recommendable for dietary uses.

Resveratrol content of Palomino fino grapes: influence of vintage and fungal infection.

The objective of this study was to determine the influence of certain factors on the resveratrol content of Palomino fino grapes, cultivated in the Jerez-Xérèz-Sherry area, at the moment of harvest. The results show that the resveratrol content is highly influenced by the climatic conditions prior to the period of maturation of the fruit. On the other hand, the gray mold pressure in the vineyard, a fungal infection caused by Botrytis cinerea, increased the resveratrol contents at the early stages of fungal development. When Botrytis development was extensive, the resveratrol content tended to decrease in the juice but tended to increase in the skin. Physiological stress of the plant leads to increases in the resveratrol content, caused as much by the climatic conditions of the vintage as by biotic factors. In this case resveratrol is present mainly in the glycosylated form.

Chemical and biochemical transformations during the industrial process of sherry vinegar aging.

The work described here concerns a study of the chemical and biochemical transformations in sherry vinegar during the different aging stages. The main factors that contribute to the nature and special characteristics of sherry vinegar are the raw sherry wine, the traditional process of acetic acid fermentation in butts (the solera system), and the physicochemical activity during the aging process in the solera system. A number of chemical and biochemical changes that occur during sherry vinegar aging are similar to those that take place in sherry wine during its biological activity process (where the wine types obtained are fino and manzanilla) or physicochemical activity process (to give oloroso wines). Significant increase in acetic acid levels was observed during the biological activity phase. In addition, the concentrations of tartaric, gluconic, succinic, and citric acids increased during the aging, as did levels of amino acids and acetoin. A color change was also produced during this stage. Glycerol was not consumed by acetic acid bacteria, and levels of higher alcohols decreased because of the synthesis of acetates. On the other hand, in the physicochemical phase the microbiological activity was lower. Concentrations of some cations increased because of evaporation of water through the wood. A color change was also produced in this stage. Concentrations of different amino acids decreased because of reaction with carbonyl compounds. A precipitation of potassium with tartaric acid was also observed.