Production of volatile compounds by yeasts using hydrolysed grape seed oil obtained by immobilized lipases in continuous packed-bed reactors.

Lipases CAL-B, TLL, and RML were used in the synthesis of free fatty acids of grape seed oil as heterogeneous substrate. The best enzyme was used to optimize the reaction variables temperature, enzyme content, and molar ratio of water:oil in batch reactions using experimental planning. The ideal conditions to produce free fatty acids using pure RML were 45 °C, 12:1 substrate molar ratio, and 15% enzyme, resulting in 66% of oil hydrolysis and a productivity of 0.54 mol L-1 min-1 in 4 h of reaction at 180 rpm. Repeated batches of reaction were performed testing the operational stability of RML, results showing that this enzyme could be used for at least 20 cycles keeping more than 80% of its initial activity, suggesting its potential use in industrial processes. The synthesis of free fatty acids was then evaluated in continuous reactions using packed-bed reactor (PBR). The highest productivity in the continuous process was 6.85 mol L-1 min-1, using only RML, showing an operational stability higher than 80% of its initial conversion capacity after 11 days of operation, at a flow rate of 0.13 mL min-1 at 45 °C. We evaluated the use of this hydrolyzed oil as substrate for lactone bioproduction using Galactomyces geotrichum UFMG-CM-Y3276, G. geotrichum UFMG-CM-Y3558, and Geotrichum klebahnii UFMG-CM-Y3014 screened for their oil-hydrolysis ability. Volatile compounds were qualitatively identified in GC-MS as γ-octalactone and γ-nonalactone.

Mold-Ripened Soft Cheeses Fortified with Date Palm Fruit Product as Functional Dairy Products.

Date fruit based products are gaining popularity among the consumers in almost all date growing countries due to its added nutritional value. Therefore, novel products were developed by combining two types of foods i.e., soft ripened cheeses and date fruit syrups or date powder. This study is the first to report the surface mold-ripened cheese production with date syrup and date powder. Model cheeses were prepared from pasteurized milk inoculated with Streptococcus thermophilus, Penicillium camemberti and Geotrichum candidum. Date syrup-1, date syrup-2, date powder or the date mixture were added at the stage of curdling. Based on the kinetic growth of the microbial groups in all the treatments, there was no change in the growth of these in various date palm product. On the contrary It may be said that addition of the date fruit product supports their growth. After 35 days, the amounts of total poly phenols were 128.3 ± 1.01, 81.8 ± 1.11, 33.5 ± 2.19, 156.23 ± 1.27 mg GAE/100 g in the cheeses support with date syrup-1, date syrup-2, date powder or the date mixture, respectively. Antioxidant activity of date fruits ranged from 80.13 IC50 (date syrup-2) to 82.23 IC50 (date syrup-1). Based on the chemical characteristics and sensory analysis, the study results showed the potential for innovative application of date products for developing new functional dairy products as an ideal medium for the delivery of biological active compounds with beneficial health effects over.

In vitro and in vivo antifungal activity of a water-dilutable cassia oil microemulsion against Geotrichum citri-aurantii.

BACKGROUND: Recently, food-grade microemulsions have been of increasing interest to researchers and have shown great potential in industrial applications. In this study a food-grade water-dilutable microemulsion system with cassia oil as oil, ethanol as cosurfactant, Tween 20 as surfactant and water was developed and its antifungal activity in vitro and in vivo against Geotrichum citri-aurantii was assessed. RESULTS: The phase diagram results confirmed the feasibility of forming a water-dilutable microemulsion based on cassia oil. One microemulsion formulation, cassia oil/ethanol/Tween 20 = 1:3:6 (w/w/w), was selected with the capability to undergo full dilution with water. The average particle size was 6.3 nm. The in vitro antifungal experiments showed that the microemulsion inhibited fungal growth on solid medium and prevented arthroconidium germination in liquid medium and that cassia oil had stronger activity when encapsulated in the microemulsion. The in vivo antifungal experiments indicated that the water-dilutable microemulsion was effective in preventing postharvest diseases of citrus fruits caused by G. citri-aurantii. CONCLUSION: The results of this study suggest a promising utilisation of water-dilutable microemulsions based on essential oils for the control of postharvest diseases.

Sequential use of ammonium and leucine as nitrogen sources during growth of Geotrichum candidum on a glucose based medium / Uso secuencial del amonio y leucina como fuentes de nitrógeno durante el crecimiento de Geotrichum candidum en un medio basado en glucosa

Geotrichum candidum growth on ammonium and leucine as nitrogen sources and glucose as a carbon source was examined. A clear preference of G. candidum for ammonium over leucine as a nitrogen source was shown. Indeed, ammonium was completely exhausted at the end of exponential growth after less than 35 hrs of culture; in contrast only 5 percent of leucine was concomitantly assimilated. Growth continued at slower rates on glucose and leucine as carbon and nitrogen sources respectively, and at the end of culture (185 hrs), leucine was completely exhausted.

Antifungal activity of thyme oil against Geotrichum citri-aurantii in vitro and in vivo.

AIMS: To investigate antifungal effect of thyme oil on Geotrichum citri-aurantii arthroconidia germination and germ tube elongation, to reveal effects of thyme oil on morphological structures on fungal hyphae and arthroconidia and to assess potential bio-control capacities of thyme oil against disease suppression in vivo conditions. METHODS AND RESULTS: Thyme oil controlled the growth of G. citri-aurantii effectively. Arthroconidia germination and germ tube elongation in potato dextrose broth was greatly inhibited by thyme oil. At 600 microl l(-1), it inhibited the germination of about 94% of the arthroconidia and the germ tube length was only 4.32 +/- 0.28 microm. Observations using light microscope, scanning electron microscope and transmission electron microscope revealed ultrastructural modifications caused by thyme oil that included markedly shrivelled and crinkled hyphae and arthroconidia, plasma membrane disruption and mitochondrial disorganization. Thyme oil applied to 'Satsuma' mandarin oranges that had been artificially wounded and inoculated with G. citri-aurantii reduced sour rot from 78.1% among untreated control fruit to 14.1% after 5 days at 26 degrees C. Thyme oil applied to intact fruits reduced the decay from 76% among untreated control fruit to 35% after 30 days at 20 degrees C. Thyme oil treatment did not harm 'Satsuma' mandarin oranges when they were examined after treatment and storage at 20 degrees C for 30 days. CONCLUSIONS: Thyme oil may provide an alternative means of controlling postharvest sour rot on citrus fruit. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of such essential oil may constitute an important alternative to synthetic fungicides. They can be exploited in commercial production and applied under storage and greenhouse conditions.

Production of tobacco aroma from lutein. Specific role of the microorganisms involved in the process.

A mixed culture formed by Bacillus sp. and Geotrichum sp. produced tobacco aroma compounds from the carotenoid lutein through the formation of the intermediate beta-ionone. Both microorganisms can grow independently in a medium supplemented with lutein, but only Geotrichum produces beta-ionone. This intermediate was incorporated by the bacilli, converted to aroma and this product excreted to the culture medium. Bacillus sp. did not utilize beta-ionone for growth but modified it. We conclude that, in the bioconversion of lutein to products with tobacco aroma, Geotrichum sp. is involved in carotenoid oxidation to produce beta-ionone and Bacillus sp. is responsible for the norisoprenoid reduction to produce 7,8-dihydro-beta-ionone and 7,8-dihydro-beta-ionol.

Production of type A trichothecenes and enniatin B by Fusarium sambucinum Fuckel sensu lato.

Twenty-nine Fusarium isolates, representing three new taxa originated by Nirenberg from F. sambucinum Fuckel sensu lato, namely: F. sambucinum Fuckel sensu stricto, F. venenotum Nirenb., and F. torulosum (Berk. & Curt.) Nirenb., were tested for in vitro production of toxic secondary metabolites on autoclaved corn kernels. F. sambucinum sensu stricto was able to produce type A trichothecenes and enniatin B (EB). In particular, amongst the 14 isolates tested, 5 produced only diacetoxyscirpenol (DAS) (up to 700 micrograms/g); 1 produced only neosolaniol (NEOS) (250 micrograms/g); 2 produced T-2 toxin (T-2) + NEOS (up to 175 and 150 micrograms/g, respectively); 1 produced NEOS + DAS (300 and 100 micrograms/g, respectively); and 5 produced DAS + EB (up to 500 and 140 micrograms/g, respectively). All six isolates of F. venenotum were able to produce only DAS (up to 100 micrograms/g). F. torulosum produced no trichothecenes, but four out of nine tested isolates were able to produce EB (up to 140 micrograms/g). Zearalenones and type B trichothecenes were not found. The toxicity of the culture extracts towards Artemia salina L. was correlated in general with the occurrence of the above toxins, except for some F. torulosum strains. However, the lack of correlation between the amounts of toxins recovered and toxic activity observed in the Geotrichum candidum Link ex Pers. and A. salina assays suggested the presence of unknown toxic compounds.

A new N-nitroso compound, N-3-methylbutyl-N-1-methylacetonylnitrosamine, in corn-bread inoculated with fungi.

A new N--nitroso compound, N--1--methylacetonyl--N--3--methylbutylnitrosamine (MAMBNA) is found in corn-bread inoculated with the common fungi, such as Fusarium moniliforme, Geotrichun candidum, Aspergillus terreus or A. flavipes, encountered in food of Lin Xian County, Henan Province. The preliminary identification of this compound with TLC has been confirmed by GC-MS analysis. Furthermore, we have synthesized the MAMBNA and the chemical analysis shows that it is identical with the MAMBNA isolated from the corn-bread extract. In addition to the MAMBNA, dimethylnitrosamine, diethylnitrosamine and methylbenzylnitrosamine are formed also in the fungus-inoculated corn-bread after 8-day incubation and an addition of a small amount of sodium nitrite. The presence of precursor compounds for the formation of nitrosamine in the mouldy maize flour and their significance in respect to the etiology of esophageal cancer in high-risk areas have been discussed.