Polyols Induce the Production of Antifungal Compounds by Lactobacillus plantarum.

Mycotoxins may be present in nuts, coffee, cereals, and grapes, among other products. Increasing concerns about human health and environmental protection have driven the application of biological control techniques that can inhibit fungal contaminants. In this study, the growth inhibition of the ochratoxigenic fungus Aspergillus carbonarius Ac 162 was evaluated using 5 lactic acid bacteria (LAB). The LAB studied were Lactobacillus plantarum MZ801739 (J), Lactobacillus plantarum MZ809351 (31) and Lactobacillus plantarum MZ809350 (34), isolated in the Ivory Coast, and Lactobacillus plantarum MN982928 (3) and Leuconostoc citreum MZ801735 (23), isolated in Mexico. J, 31, 34, 3 and 23 are the internal strain codes from our laboratory. LAB were cultivated in De Man, Rogosa and Sharpe (MRS) broth, and different polyols (glycerol, mannitol, sorbitol, and xylitol) were added to the culture broth to stimulate the production of antifungal compounds. The fungal inhibition studies were performed using the poisoned food technique. The highest inhibition of A. carbonarius growth was obtained by cultivating L. plantarum MZ809351 in the presence of xylitol and glycerol. Under these conditions, 1 L of the L. plantarum MZ809351 cultures were used to identify antifungal compounds. The compounds were concentrated by solid-phase extraction and then characterized by GC-MS. In addition to 9-octadecenoic acid, 3 diketopiperazines or cyclic dipeptides were identified, including cyclo (Leu-Leu), cyclo (Pro-Gly) and cyclo (Val-Phe), which were compounds related to microbial antifungal activities. Xylitol and glycerol induced the production of these antifungal compounds against A. carbonarius Ac 162. On the other hand, adding xylitol and glycerol to the MRS broth reduced the Ochratoxin A (OTA) content to 56.8 and 54.7%, respectively. This study shows the potential for using L. plantarum MZ809351 as a biocontrol agent to prevent the growth of A. carbonarius and reduce the production of OTA in foods.

Sucrose Hydrolysis in a Continuous Packed-Bed Reactor with Auto-immobilise Aspergillus niger Biocatalyst Obtained by Solid-State Fermentation.

Invertase from Aspergillus niger C28B25 was produced by solid-state fermentation (SSF). Fermented solids were used directly as a biocatalyst for batch and continuous hydrolysis of sucrose in a packed-bed reactor under different operational conditions with various temperatures, sucrose concentrations, and feed flow rates. The SSF allowed obtaining a biocatalyst with an invertase activity of 82.2 U/g db. The biocatalyst maintained its activity in the range of 40 to 70 °C for at least 70 h of continuous operation. In a 20-mL packed bed reactor, the highest hydrolysis rate (12.3 g/g db h) was obtained at 40 °C with 2 M sucrose. Continuous hydrolysis in 20-mL and 200-mL reactors at 60 °C led to sucrose hydrolysis above 60% (8.5 residence times) and above 55% (4.5 residence times), respectively. The auto-immobilised biocatalyst produced by SSF without recovery, purification, and immobilisation stages offers an economical alternative for developing accessible biocatalysts that can be applied in batch or continuous sucrose hydrolysis processes. This study shows the potential of biocatalyst production by SSF for other enzymatic systems.

Biosurfactants: The green generation of speciality chemicals and potential production using Solid-State fermentation (SSF) technology.

Surfactants are multipurpose products found in most sectors of contemporary industry. Their large-scale manufacturing has been mainly carried out using traditional chemical processes. Some of the chemical species involved in their production are considered hazardous and some industrial processes employing them categorised as "having potential negative impact on the environment". Biological surfactants have therefore been generally accepted worldwide as suitable sustainable greener alternatives. Biosurfactants exhibit the same functionalities of synthetic analogues while having the ability to synergize with other molecules improving performances; this strengthens the possibility of reaching different markets via innovative formulations. Recently, their use was suggested to help combat Covid-19. In this review, an analysis of recent bibliography is presented with descriptions, statistics, classifications, applications, advantages, and challenges; evincing the reasons why biosurfactants can be considered as the chemical specialities of the future. Finally, the uses of the solid-state fermentation as a production technology for biosurfactants is presented.

Microcultures of lactic acid bacteria: characterization and selection of strains, optimization of nutrients and gallic acid concentration.

Eighteen lactic acid bacteria (LAB) strains, isolated from coffee pulp silages were characterized according to both growth and gallic acid (GA) consumption. Prussian blue method was adapted to 96-well microplates to quantify GA in LAB microcultures. Normalized data of growth and GA consumption were used to characterize strains into four phenotypes. A number of 5 LAB strains showed more than 60% of tolerance to GA at 2 g/l; whereas at 10 g/l GA growth inhibition was detected to a different extent depending on each strain, although GA consumption was observed in seven studied strains (>60%). Lactobacillus plantarum L-08 was selected for further studies based on its capacity to degrade GA at 10 g/l (97%). MRS broth and GA concentrations were varied to study the effect on growth of LAB. Cell density and growth rate were optimized by response surface methodology and kinetic analysis. Maximum growth was attained after 7.5 h of cultivation, with a dilution factor of 1-1/2 and a GA concentration between 0.625 and 2.5 g/l. Results indicated that the main factor affecting LAB growth was GA concentration. The main contribution of this study was to propose a novel adaptation of a methodology to characterize and select LAB strains with detoxifying potential of simple phenolics based on GA consumption and tolerance. In addition, the methodology presented in this study integrated the well-known RSM with an experimental design based on successive dilutions.

Continuous ethyl oleate synthesis by lipases produced by solid-state fermentation by Rhizopus microsporus.

Lipases produced by solid-state fermentation were used directly as biocatalysts for continuous synthesis of ethyl oleate in a continuously stirred tank reactor. The effect of biocatalyst reutilisation, molar ratio of substrates, agitation rate and feed rate on the esterification of oleic acid with ethanol were investigated. The catalyst maintained 90% conversion for four batch cycles with a 1:2 molar ratio (oleic acid:ethanol). Mechanical agitation at 200 and 300 rpm during 12 h of continuous reaction did not affect the biocatalytic conversion, allowing substrate conversions greater than 90% that were obtained with 50 mM oleic acid at a molar ratio of 1:2 during 14 h reaction. In contrast, substrate conversion was 70% with 100 mM oleic acid at a flow rate of 2 mL/min during 25 h of reaction. These results are promising and offer a technical alternative for the development of accessible biocatalysts that can be used in continuous operations.

On-line monitoring of Aspergillus niger GH1 growth in a bioprocess for the production of ellagic acid and ellagitannase by solid-state fermentation.

The present work describes the monitoring of CO2 production by Aspergillus niger GH1 in a bioprocess for the production of ellagitannase (EAH) and ellagic acid by solid state fermentation. Pomegranate ellagitannins, mainly punicalagin, were used as carbon source and EAH inducer. A second condition, using ellagitannins and maltose as growth promoting carbon source, was tested. The ellagic acid production was quantified and the EAH activity was assayed. The accumulated metabolites were identified by HPLC-ESI-MS/MS. Higher CO2 production (7.79mg/grams of dry material) was reached in media supplemented with maltose. Short-time lag phase (7.79h) and exponential phase (10.42h) were obtained using only ellagitannins, despite its lower CO2 production (3.79mg/grams of dry material). Without the use of maltose lower ellagic acid (11.85mg/L/h) and EAH (21.80U/L/h) productivities were reached. The use of maltose enhances the productivity of EA (33.18mg/L/h) and EAH (33.70U/L/h). Besides of punicalin and ellagic acid, two unknown compounds with mass weight of 702 and 290g/mol (ions 701 and 289m/z in negative mode, respectively) were identified and characterized by HPLC-ESI-MS/MS analysis.

Modeling of growth, lactate consumption, and volatile fatty acid production by Megasphaera elsdenii cultivated in minimal and complex media.

Use of the Pirt and Luedeking-Piret equations permits the determination of the effect of medium composition on the metabolic patterns of Megasphaera elsdenii grown in minimal and complex media with lactate as the major carbon source. To establish the significance of the parameters involved in the Pirt and Luedeking-Piret equations, a quantitative statistical criterion was proposed. In the complex medium, lactate was completely used for growth and product formation, whereas in the minimal medium a fraction of the energy obtained from lactate was used for maintenance purposes. Modeling of VFA production by the Luedeking-Piret equation showed that, independent of the type of medium, acetate and propionate are growth-associated products, while butyrate and valerate are only partially growth-associated. The growth-associated products are related to energy-yielding metabolism and the non-growth-associated products are related to the consumption of reducing equivalents.

Oxygen-rich culture conditions enhance the conidial infectivity and the quality of two strains of Isaria fumosorosea for potentially improved biocontrol processes.

BACKGROUND: In addition to high production levels of conidia, the success of entomopathogenic fungi as biological control agents depends both on their prevalence under the environmental conditions found in open fields (resistance to stress) and on the capacity of these conidia to infect pests. This study compares conidium production, infectivity and resistance to thermal and osmotic stress in two strains of Isaria fumosorosea (ARSEF 3302 and CNRCB1) grown either under a normal atmosphere (21% O2) or using enriched oxygen pulses (26% O2). RESULTS: After 180 h, the ARSEF 3302 strain with 26% O2 pulses increased conidium production nearly fivefold compared with the normal atmosphere, while conidium production by the CNRCB1 strain decreased by 50% under O2 pulses, relative to the values measured with the normal atmosphere. The conidia obtained with 26% O2 pulses had a greater germination rate and resistance to thermal and osmotic stress, in addition to improved infectivity against Galleria mellonella (Lepidoptera) larvae. These findings were associated with an increase in catalase activities for both strains. CONCLUSION: An enriched oxygen atmosphere increases the quality of conidia of both strains of I. fumosorosea, with a variable effect on conidium production.

Soluble and bound hydroxycinnamates in coffee pulp (Coffea arabica) from seven cultivars at three ripening stages.

The contents of soluble and bound hydroxycinnamates (HCAs) were analyzed in coffee pulp (CP) of seven cultivars of Coffea arabica at three different ripening stages. Methodologies for the extraction and analysis of HCAs were evaluated and improved. HCAs were present mainly in the soluble fraction (68-97%). Chlorogenic acid was the main phenolic acid (94-98%) in the soluble fraction, whereas caffeic acid was the most abundant HCA found in the bound fraction (72-88%). Small amounts of free and bound ferulic and p-coumaric acids were also detected. The content of total HCAs in CP reached the maximum concentration at the semiripe stage (7.4-25.5 mg/g CP, dw) but decreased at the ripe stage for six of the seven cultivars. These findings suggest that unripe or semiripe coffee cherries, considered as defective cherries, are a potential inexpensive source of phenolic compounds, such as chlorogenic and caffeic acids.

Biotransformation and improved enzymatic extraction of chlorogenic acid from coffee pulp by filamentous fungi.

The highest enzymatic extraction of covalent linked chlorogenic (36.1%) and caffeic (CA) (33%) acids from coffee pulp (CP) was achieved by solid-state fermentation with a mixture of three enzymatic extracts produced by Aspergillus tamarii, Rhizomucor pusillus, and Trametes sp. Enzyme extracts were produced in a practical inexpensive way. Synergistic effects on the extraction yield were observed when more than one enzyme extract was used. In addition, biotransformation of chlorogenic acid (ChA) by Aspergillus niger C23308 was studied. Equimolar transformation of ChA into CA and quinic acids (QA) was observed during the first 36 h in submerged culture. Subsequently, after 36 h, equimolar transformation of CA into protocatechuic acid was observed; this pathway is being reported for the first time for A. niger. QA was used as a carbon source by A. niger C23308. This study presents the potential of using CP to produce enzymes and compounds such as ChA with biological activities.

Biotransformation of ferulic acid to 4-vinylguaiacol by a wild and a diploid strain of Aspergillus niger.

Ferulic acid biotransformation has a number of interesting industrial uses. Ferulic acid biotransformation by the wild strain Aspergillus niger C28B25 and a diploid strain DAR2, obtained by parasexual recombination, was studied. The wild strain of A.niger C28B25 biotransforms ferulic acid to vanillic acid (VA); while the diploid strain DAR2 preferentially decarboxylates ferulic acid to 4-vinylguaiacol (4VG). The latter was identified by mass spectroscopy, (1)H and (13)C nuclear magnetic resonance spectroscopy, and quantified by HPLC. The diploid strain A.niger DAR2 and the wild strain showed a ferulic acid conversion of 64% and 36%, respectively. Molar yields show that the formation of 4VG was preferred, being as much as 4.4 times higher than the formation of VA in diploid strain cultures. Differential regulation of enzymes involved in the biotransformation of ferulic acid may explain the accumulation of 4VG by diploid DAR2. This strain produced both 4VG and VA.

Lactase production by solid-state cultivation of Kluyveromyces marxianus CDBBL 278 on an inert support: effect of inoculum, buffer, and nitrogen source.

A study was carried out to select the conditions for cultivation of Kluyveromyces marxianus CDBBL 278 in solid-state culture (SSC) using polyurethane foam (PUF) as an inert support. PUF was impregnated with culture media containing lactose (50 g/L) as the carbon and energy source. Evaluation of culture parameters during different growth phases was carried out by respirometry. The effect of inoculum level, buffer capacity of the medium, and nitrogen source upon the yield of biomass on lactose (Yx/s) and production of lactase and inulinase was investigated. The highest lactase titre was achieved with an inoculum level of 1 x 10(7) cells per gram of wet matter (gwm) and 20% of the total nitrogen source provided as urea. The best biomass yield (0.37) was obtained when less than 40% of the total nitrogen was provided as urea. Using potassium phosphate allowed 90% substrate consumption in 30 h. In the best conditions, intracellular lactase and extracellular inulinase activities of 1147.7 IU/gX and 241.6 IU/gX were obtained, respectively, with a lag phase of 13.8 h and a rate of respiratory activity (microCO2) of 0.23 +/- 0.01 h(-1). To our knowledge, this is the first report on lactase production by K. marxianus CDBBL 278 in SSC. This study gives basic information about biomass yield and enzyme production using lactose as the sole carbon source in SSC on an inert support.

Organic phase synthesis of ethyl oleate using lipases produced by solid-state fermentation.

This paper reports a study of the enzymatic esterification of oleic acid and ethanol. The reaction was catalyzed by lipases produced by solid-state fermentation with Rhizopus sp. Olive oil and perlite were used as an inducer and inert support, respectively. Synthesis of ethyl oleate was carried out in a 10-mL batch reactor with magnetic stirring. The effects of substrate ratios, biocatalyst concentration, and temperature on the reaction rate and conversion efficiency were evaluated. The highest reaction rate (1.64 mmol/L min) was reached with an oleic acid/ethanol mol ratio of 1:5 (oleic acid 50 mM:ethanol 250 mM) and 1 g of biocatalyst. Conversions approaching 100% were obtained after 60 min of reaction at 45 degrees C with n-hexane as a solvent. The initial reaction rate increased proportionally with respect to biocatalyst concentration, which suggests that the reaction rate was not controlled by mass transfer. The biocatalyst retained more than 80% of its catalytic activity after 7 months of storage at 4 degrees C. The results demonstrate that the biocatalyst produced by Rhizopus sp. in solid-state fermentation can be successfully used for ethyl oleate synthesis over short reaction periods under conditions when ethanol is in excess.

Screening of native yeast from Agave duranguensis fermentation for isoamyl acetate production

In this work, fifty yeast strains, isolated from the spontaneous alcoholic fermentation of Agave duranguensis to produce mezcal, were tested using the double coupling system. These yeasts were from the genera Pichia, Torulaspora, Saccharomyces, Kluyveromyces, Deckera, Hanseniaspora, and Candida. P. fermentans ITD00165 was the best isoamyl acetate producer, yielding 0.38 g/L of ester after incubation for 24 h, while K. marxianus ITD00211 produced 0.32 g/L of ester. Thus P. fermentans TD00165 could be considered as an excellent choice for use in optimization studies of the culture medium and bioreactor operating conditions to develop a process for biotechnological production of isoamyl acetate.

Effect of moisture content and inoculum on the growth and conidia production by Beauveria bassiana on wheat bran

The aim of the present work was to study the effect of moisture content and inoculum on the growth and conidia production by Beauveria bassiana on wheat bran (WB).The highest growth rate of B. bassiana 885.2 on WB media was obtained at a w=1.0, with no detected growth at a w < 0.97. Solid-state fermentation (SSF) using WB (66 percent moisture; a w=1.0) achieved a maximal yield of 1.18x10 10 conidia per gram of dry substrate (gds). This yield decreased one order of magnitude with higher moisture contents or the addition of sugarcane bagasse (SCB) as a texturiser. In SSF using WB (66 percent humidity),the time to obtain a yield of 1x10(10) conidia/gds, referred to as t10, could be predicted using a model considering common inoculum levels and maximal yields. For instance, t10 was 285 h with an inoculum of 1x10(6) conidia/gds; however, t10 was reduced to 232 h and 148 for inocula of 7x10(6) and 5x10(7) conidia/gds, respectively. The estimation of t10 values allowed both comparison between the cultures and prediction of harvesting times in production processes. Values for hydrophobicity were within 90 and 92 percent, whereas viability averages were around 70 percent for all the cultures