Grape and wine analysis: Oenologists to exploit advanced test kits.
Charnock, S. C. & McCleary, B. V. (2005). Revue des Enology, 117, 1-5.
It is without doubt that testing plays a pivotal role throughout the whole of the vinification process. To produce the best possible quality wine and to minimise process problems such as “stuck” fermentation or troublesome infections, it is now recognised that if possible testing should begin prior to harvesting of the grapes and continue through to bottling. Traditional methods of wine analysis are often expensive, time consuming, require either elaborate equipment or specialist expertise and frequently lack accuracy. However, enzymatic bio-analysis enables the accurate measurement of the vast majority of analytes of interest to the wine maker, using just one piece of apparatus, the spectrophotometer (see previous issue No. 116 for a detailed technical review). Grape juice and wine are amenable to enzymatic testing as being liquids they are homogenous, easy to manipulate, and can generally be analysed without any sample preparation.
Megazyme “advanced” wine test kits general characteristics and validation.
Charnock, S. J., McCleary, B. V., Daverede, C. & Gallant, P. (2006). Reveue des Oenologues, 120, 1-5.
Many of the enzymatic test kits are official methods of prestigious organisations such as the Association of Official Analytical Chemicals (AOAC) and the American Association of Cereal Chemists (AACC) in response to the interest from oenologists. Megazyme decided to use its long history of enzymatic bio-analysis to make a significant contribution to the wine industry, by the development of a range of advanced enzymatic test kits. This task has now been successfully completed through the strategic and comprehensive process of identifying limitations of existing enzymatic bio-analysis test kits where they occurred, and then using advanced techniques, such as molecular biology (photo 1), to rapidly overcome them. Novel test kits have also been developed for analytes of emerging interest to the oenologist, such as yeast available nitrogen (YAN; see pages 2-3 of issue 117 article), or where previously enzymes were simply either not available, or were too expensive to employ, such as for D-mannitol analysis.
Production of L-lactic acid from a green microalga, Hydrodictyon reticulum, by Lactobacillus paracasei LA104 isolated from the traditional Korean food, makgeolli.
Nguyen, C. M., Kim, J. S., Hwang, H. J., Park, M. S., Choi, G. J., Choi, Y. H., Jang, K. S. & Kim, J. C. (2012). Bioresource Technology, 110, 552-559.
The freshwater microalga, Hydrodictyon reticulum, that contained 47.5% reducing sugars including 35% glucose was used as substrate for the production of L-lactic acid (LA) by LA-producing bacteria. Lactobacillus paracasei LA104 was selected for fermentation in a 5-l fermentor since it was able to grow at pH 3, 60 g LA/l, 200 g glucose/l, 125 g NaCl/l, and 45°C and produced over 97.3% optically pure L-lactic acid with glucose as a substrate. Simultaneous saccharification and cofermentation from H. reticulum to L-LA using LA104 was investigated in a jar fermentor. The yield reached 46 g/100 g H. reticulum dry material, with a final concentration of 37.11 g/l and a productivity of 1.03 g/l/h. This is the first report of the production of L-LA from a microalga, and H. reticulum could be a potential feedstock for large-scale production of L-LA by LA104.
D-Lactic acid production from dry biomass of Hydrodictyon reticulatum by simultaneous saccharification and co-fermentation using Lactobacillus coryniformis subsp. torquens.
Nguyen, C. M., Kim, J. S., Song, J. K., Choi, G. J., Choi, Y. H., Jang, K. S. & Kim, J. C. (2012). Biotechnology Letters, 34(12), 2235-2240.
D-Lactic acid production from dry biomass of the microalga, Hydrodictyon reticulatum, was carried out in a 5-l jar fermentor (initial pH 6, 34°C using CaCO3 as a neutralizing agent) through simultaneous saccharification and co-fermentation using the Lactobacillus coryniformis subsp. torquens. After 36 h, 36.6 g lactic acid/l was produced from 80 g H. reticulatum/l in the medium containing 3 g yeast extract/l and 3 g peptone/l in the absence of mineral salts. The maximum productivity, average productivity and yield were 2.38 g/l h, 1.02 g/l h and 45.8%, respectively. The optical purity of D-Lactic acid ranged from 95.8–99.6%. H. reticulatum is thus a promising biomass material for the production of D-Lactic acid.
Modelling the Effect of Different Substrates and Temperature on the Growth and Lactic Acid Production by Lactobacillus amylovorus DSM 20531T in Batch Process.
Trontel, A., Baršić, V., Slavica, A., Santek, B. & Novak, S. (2010). Food Technology & Biotechnology, 48(3), 351-361.
Amylolytic lactic acid bacterium Lactobacillus amylovorus DSM 20531T utilised glucose, sucrose and starch as a sole carbon and energy source. The three substrates were completely depleted from MRS medium during batch cultivations carried out in a laboratory scale stirred tank bioreactor at constant temperature (40°C) and pH value (5.5). Under the tested conditions, the bacterium was capable of conducting simultaneously starch hydrolysis and fermentation. A mixture of two stereoisomers, D-(-)- and L-(+)-lactic acid, was produced in all cases by highly efficient homofermentative bioprocess with 0.93 to 1 g of lactate produced per g of total (consumed) substrate. The effect of temperature on the kinetics of cell growth and lactic acid production by the amylolytic strain in the starch-containing medium was also investigated. Efficient simultaneous saccharification and fermentation (SSF) was obtained at 35, 40 and 45°C with completely degraded complex carbohydrate in 8 to 12 h and the product yield coefficient in the range from 0.91 to 0.93 g/g. Maximum values for substrate consumption rate (0.89 h-1), maximum specific growth rate (0.87 h-1), product formation rate (2.01 h-1), and productivity of lactic acid (1.45 g/(Uh)) were obtained at 45°C, while maximum biomass concentration (4.38 g/L) was attained at 40°C. The ratio of the two stereoisomeric forms of produced lactic acid was strongly affected by the temperature. Unstructured kinetic model was used to describe the consumption of the three substrates, bacterial biomass formation and lactic acid production by L. amylovorus DSM 20531T. The dependence of biokinetic parameters on temperature was described by cardinal temperature model. The applied models successfully predicted all experimental data.
Engineering a cyanobacterial cell factory for production of lactic acid.
Angermayr, S. A., Paszota, M. & Hellingwerf, K. J. (2012). Applied and Environmental Microbiology, 78(19), 7098-7106.
Metabolic engineering of microorganisms has become a versatile tool to facilitate production of bulk chemicals, fuels, etc. Accordingly, CO2 has been exploited via cyanobacterial metabolism as a sustainable carbon source of biofuel and bioplastic precursors. Here we extended these observations by showing that integration of an ldh gene from Bacillus subtilis (encoding an L-lactate dehydrogenase) into the genome of Synechocystis sp. strain PCC6803 leads to L-lactic acid production, a phenotype which is shown to be stable for prolonged batch culturing. Coexpression of a heterologous soluble transhydrogenase leads to an even higher lactate production rate and yield (lactic acid accumulating up to a several-millimolar concentration in the extracellular medium) than those for the single ldh mutant. The expression of a transhydrogenase alone, however, appears to be harmful to the cells, and a mutant carrying such a gene is rapidly outcompeted by a revertant(s) with a wild-type growth phenotype. Furthermore, our results indicate that the introduction of a lactate dehydrogenase rescues this phenotype by preventing the reversion.
Sourdough-leavened bread improves postprandial glucose and insulin plasma levels in subjects with impaired glucose tolerance.
Maioli, M., Pes, G. M., Sanna, M., Cherchi, S., Dettori, M., Manca, E. & Farris, G. A. (2008). Acta Diabetologica, 45(2), 91-96.
Sourdough bread has been reported to improve glucose metabolism in healthy subjects. In this study postprandial glycaemic and insulinaemic responses were evaluated in subjects with impaired glucose tolerance (IGT) who had a meal containing sourdough bread leavened with lactobacilli, in comparison to a reference meal containing bread leavened with baker yeast. Sixteen IGT subjects (age range 52–75, average BMI 29.9 ± 4.2 kg/m²) were randomly given a meal containing sourdough bread (A) and a meal containing the reference bread (B) in two separate occasions at the beginning of the study and after 7 days. Sourdough bread was leavened for 8 h using a starter containing autochthonous Saccharomyces cerevisiae and several bacilli able to produce a significant amount of D-and L-lactic acid, whereas the reference bread was leavened for 2 h with commercial baker yeast containing Saccharomyces cerevisiae. Plasma glucose and insulin levels were measured at time 0, 30, 60, 120, and 180 min. In IGT subjects sourdough bread induced a significantly lower plasma glucose response at 30 minutes (p = 0.048) and a smaller incremental area under curve (AUC) Δ 0–30 and Δ 0–60 min (p = 0.020 and 0.018 respectively) in comparison to the bread leavened with baker yeast. Plasma insulin response to this type of bread showed lower values at 30 min (p = 0.045) and a smaller AUC Δ 0–30 min (p = 0.018). This study shows that in subjects with IGT glycaemic and insulinaemic responses after the consumption of sourdough bread are lower than after the bread leavened with baker yeast. This effect is likely due to the lactic acid produced during dough leavening as well as the reduced availability of simple carbohydrates. Thus, sourdough bread may potentially be of benefit in subjects with impaired glucose metabolism.
Homo-fermentative production of D-lactic acid by Lactobacillus sp. employing casein whey permeate as a raw feed-stock.
Prasad, S., Srikanth, K., Limaye, A. M. & Sivaprakasam, S. (2014). Biotechnology Letters, 36(6) 1303-1307.
Casein whey permeate (CWP), a lactose-enriched dairy waste effluent, is a viable feed stock for the production of value-added products. Two lactic acid bacteria were cultivated in a synthetic casein whey permeate medium with or without pH control. Lactobacillus lactis ATCC 4797 produced D-lactic acid (DLA) at 12.5 g l-1 in a bioreactor. The values of Leudking–Piret model parameters suggested that lactate was a growth-associated product. Batch fermentation was also performed employing CWP (35 g lactose l-1) with casein hydrolysate as a nitrogen supplement in a bioreactor. After 40 h, L. lactis produced 24.3 g lactic acid l-1 with an optical purity >98%. Thus CWP may be regarded as a potential feed-stock for DLA production.
Effect of thermal processing during yogurt production upon the detection of staphylococcal enterotoxin B.
Principato, M., Boyle, T., Njoroge, J., Jones, R. L. & O'Donnell, M. (2009). Journal of Food Protection®, 72(10), 2212-2216.
This research was conducted to examine the inherent properties of yogurt contaminated with staphylococcal enterotoxin B (SEB). Two types of yogurts were produced for this study. Type I yogurts were produced by adding SEB at the start of yogurt production, and type II yogurts were produced by adding SEB after the milk base had been boiled. Biochemical characteristics inherent to yogurt, including pH, lactic acid and acetaldehyde concentrations, were analyzed weekly for each batch beginning at a time just after production and throughout a storage period of at least 4 weeks. The presence of toxin during yogurt production did not result in any significant biochemical or physical changes in yogurt. However, we were unable to detect SEB toxin in type I yogurt using a commercially available enzyme-linked immunosorbent assay (ELISA). In contrast, SEB was easily detectable by our ELISA in type II yogurt samples. Higher levels of SEB were recovered from type II yogurt that had been stored for 1 week than from type II yogurt that had been stored for any other length of time. These results indicate that the biochemical characteristics of yogurt did not change significantly (relative to control yogurt) in the presence of either thermally processed SEB or native SEB. However, the ability to detect SEB by ELISA was dependent on whether the toxin had been processed.
The effect of ciliate fauna composition on murein content and mureinolytic activity in the rumen of sheep.
Bełżecki, G., Miltko, R., Kwiatkowska, E., Kowalik, B. & Michałowski, T. (2012). Journal of Animal and Feed Sciences, 21(1), 65-76.
The effect of the ciliates, Eudiplodinium maggii, Diploplastron affine and Entodinium caudatum, and natural protozoal fauna on the ruminal murein concentration and mureinolytic activity was examined on three rams, repeatedly defaunated and refaunated with Eudiplodinium maggii, Diploplastron affine, Entodinium caudatum and natural protozoal fauna. The number of ciliates varied from 18 (E. maggii) to 334 x 103/g rumen content (natural fauna). The murein concentration fluctuated between 180 and 277 mg/g dry matter (DM). The establishment of ciliates in the rumen of defaunated sheep decreased the murein content by 28-35% (P<0.05). Mureinolytic activity varied from 2.2 and 5.7 μg/g DM of rumen fluid/min and was the lowest in defaunated sheep and the highest in animals faunated with E. caudatum. The protozoa increased this activity from 32 (E. maggii) to 159% (E. caudatum). All examined parameters showed diurnal variations. The ciliate number was the greatest just before feeding and the smallest 4 h thereafter. The fluctuation pattern in murein content was inverse to that of protozoa concentration and mureinolytic activity.
Solid state fermentation with lactic acid bacteria to improve the nutritional quality of lupin and soybean.
Bartkiene, E., Krungleviciute, V., Juodeikiene, G., Vidmantiene, D. & Maknickiene, Z. (2015). Journal of the Science of Food and Agriculture, 95(6), 1336-1342.
BACKGROUND: The ability of bacteriocin-like inhibitory substance (BLIS)-producing lactic acid bacteria (LAB) to degrade biogenic amines as well as to produce L(+) and D(−)-lactic acid during solid state fermentation (SSF) of lupin and soya bean was investigated. In addition, the protein digestibility and formation of organic acids during SSF of legume were investigated. RESULTS: Protein digestibility of fermented lupin and soya bean was found higher on average by 18.3% and 15.9%, respectively, compared to untreated samples. Tested LAB produced mainly L-lactic acid in soya bean and lupin (D/L ratio 0.38–0.42 and 0.35–0.54, respectively), while spontaneous fermentation gave almost equal amounts of both lactic acid isomers (D/L ratio 0.82–0.98 and 0.92, respectively). Tested LAB strains were able to degrade phenylethylamine, spermine and spermidine, whereas they were able to produce putrescine, histamine and tyramine. CONCLUSIONS: SSF improved lupin and soya bean protein digestibility. BLIS-producing LAB in lupin and soya bean medium produced a mixture of D- and L-lactic acid with a major excess of the latter isomer. Most toxic histamine and tyramine in fermented lupin and soya bean were found at levels lower those causing adverse health effects. Selection of biogenic amines non-producing bacteria is essential in the food industry to avoid the risk of amine formation.