John S. Read

Application of very high gravity technology to the cofermentation of sweet stem sorghum juice and sorghum grain.

Ethanol production from mixtures of sweet stem sorghum juice and sorghum grain was investigated under normal and very high gravity (VHG) fermentation conditions. Fermentation was carried out using Saccharomyces cere6isiae yeast strain N96 at 30°C. For VHG fermentation, sucrose was added to the sweet sorghum juice to obtain a concentration of 34 g per 100 ml of dissolved solids. Fermentation was carried out for 96 h using malted and unmalted milled sorghum grain from sorghum cultivars DC-75 and SV-2. Under VHG conditions, maximum ethanol levels were about 16.8% (v:v) and 11% (v:v) for media containing malted and unmalted milled sorghum grain, respectively. Although fermentation did not occur to completion, levels of ethanol obtained under VHG conditions were three times higher than the levels obtained under normal fermentation conditions. Under VHG conditions, about 8 g:100 ml of dissolved solids remained in the fermentation media after ethanol production had ceased while under normal fermentation conditions, about 4 g:100 ml of dissolved solids remained unused in the fermentation media. There was an initial decline in free amino nitrogen (FAN) levels up to 34 h followed by an increase up to 96 h under VHG fermentation conditions. Levels of assayable proanthocyanidins (PAs) from sorghum cultivar DC-75 were reduced during fermentation.

FATTY ACID SELECTIVITY OF A LIPASE PURIFIED FROM VERNONIA GALAMENSIS SEED

Vernonia galamensis is an annual herb whose seed oil contains high levels of an epoxy fatty acid, vernolic (cis-12,13-epoxy cis-9-octadecenoic) acid. The seed also contains lipase activity in the dormant state. A lipase was purified from the seed and its substrate specificity studied in isooctane. The lipase shows pronounced selectivity for the native triacylglycerol, trivernolin. The rate of hydrolysis of triolein, the corresponding non epoxy triacylglycerol, is only 3% of that of trivernolin. In the acidolysis of tricaprylin using a mixture of fatty acids, the Vernonia lipase also showed selectivity for vernolic acid. Michaelis-Menten kinetics of the hydrolysis of triacylglycerols revealed that the observed high selectivity of the Vernonia lipase for trivernolin was mainly due to a higher Vmax for trivernolin. The Vmax value for the hydrolysis of trivernolin was 5 times higher than that for triolein. This novel substrate specificity is an adaptation by the seed lipase to the triacylglycerols of the seed oil that contain up to 80% vernolic acid.

The effects of sorghum proanthocyanidins on digestive enzyme activity in vitro and in the digestive tract of chicken

The effects of sorghum grain proanthocyanidins (PAs) on the digestive enzyme activity of broiler chickens were investigated in vitro and in vivo using seven sorghum varieties grown in Zimbabwe. All seven sorghum varieties, classified as either high-PA (DC-75, Mutode, Red Swazi and Chirimaugute) or low-PA (SV2, Brown Tsweta and Chibonda), were used to assess the PA–protein binding capacity and inhibition of trypsin and amylase in vitro. Three of the varieties (Chirimaugute, Chibonda and Brown Tsweta) were subsequently used in broiler diets to test the effects of PAs on the growth performance and digestive enzyme activity of 48 broiler chicks at 42 days of age. Protein precipitation and trypsin and amylase inhibition increased (Pu2005<u20090.05) with an increase in level of PAs from the low-PA varieties (by 1–10%) to the high-PA varieties (by 40–70%). The activity of trypsin in the duodenal lumen of chicks fed the control diet was almost double that of chicks fed Chirimaugute. Amylase activity in the high-PA group was lowered significantly (Pu2005<u20090.01) relative to the control and low-PA groups. The difference between in vitro and in vivo residual enzyme activities was 10–20% for amylase and 5–10% for trypsin. Chicks fed the high-PA diet showed lower performance than chicks fed the control and low-PA diets. Mean body weight gains were 59.9, 34.4, 57.3 and 61.4 (SE 4.02) gu2009day−1, final weights were 1936.4, 1363.3, 1773.2 and 1857.0 (SE 78.5)u2009g and feed efficiencies were 1.85, 2.26, 1.65 and 2.13 (SE 0.014) for the control, Chirimaugute, Brown Tsweta and Chibonda groups respectively. The results indicate that PA–enzyme interaction, in addition to dietary protein–PA binding, contributes to the poor performance of chickens fed high-PA sorghum diets. n n n n© 2000 Society of Chemical Industry

[12] Vernonia lipase: A plant lipase with strong fatty acid selectivity

Publisher Summary Lipases are useful tools in lipid processing. One important advantage of lipase-catalyzed processing compared to chemical methods is the inherent selectivity of the enzymatic reactions. It has been shown that some plant seeds contain lipases that show selectivity for the most common fatty acids in that particular kind of seed. It can thus be of interest to study lipases from plant seeds that contain unusual fatty acids. This chapter describes a lipase from seed of Vernonia galamensis . These seeds contain about 40% oil and the oil contains up to 80% vernolic acid. Much of the vernolic acid is present in the form of trivernolin. The chapter describes the purification and properties of the lipase as well as purification and properties of trivernolin and vernolic acid, which are used in the studies of the fatty acid selectivity of the lipase.

Lysis of erythrocytes by Trichomonas vaginalis.

The in vitro hemolytic activity of 4 isolates ofTrichomonas vaginalis was investigated. Repetitive hemolysis assays of any one isolate showed cyclical fluctuations in hemolytic activity, varying over 24 hr of continuous culture. Maximal hemolytic activity was detected using trichomonads in the lag phase of the growth cycle. Investigations showed that hemolysis was a contact-dependent phenomenon and microscopic investigation of samples showed a significant correlation between hemolysis and attachment of erythrocytes to the trichomonad surface. Quantitative data from cytoadherence assays using [51Cr]-labeled erythrocytes were consistent with these observations. It is suggested that hemolytic activity is dependent upon adherence of red blood cells to the surface ofT. vaginalis.

Triacylglycerols of Vernonia galamensis seed oil

Abstract Separation methods using silica gel column chromatography and preparative thin layer chromatography were employed to prepare pure triacylglycerol fractions of the oil from Vernonia galamensis seeds. Pure vernolic acid (12,13-epoxy-octadec- cis -9-enoic acid) was prepared by enzymatic hydrolysis of the chromatographically purified major triacylglycerol, trivernolin, using a commercially available immobilised lipase in a non-polar organic solvent. Analysis of the divernoloyl and monovernoloyl triacylglycerols with porcine pancreatic lipase indicated that vernolic acid is found mainly as the secondary ester in the divernoloyl triacylglycerol but not the monovernoloyl triacylglycerol.

Screening for plant lectins by latex agglutination tests

The latex agglutination test has been applied as a detection system for lectins, the method being especially useful in locations where the dependence on blood for hemagglutination tests could be minimised. The binding of various glycoproteins and sugars individually to the latex particles facilitated the agglutination with lectins having varying sugar specificities. The glycoproteins used were ovalbumin, horseradish peroxidase, porcine mucin and fetuin, while N-acetylglucosamine, N-acetylgalactosamine comprised the sugars used for binding to latex. The sensitivity of the latex agglutination tests was comparable with that of hemagglutination tests. Sugar binding specificity of the lectins could also be determined by inhibition of the agglutination in the presence of corresponding free sugars. The method proved to be useful in screening crude seed extracts for the presence of lectins.

Evaluation of Vernonia galamensis lipase (acetone powder) for use in biotechnology

Abstract An acetone powder was prepared from Vernonia galamensis seed. This acetone powder was used as a source of crude immobilised lipase to characterise the Vernonia lipase for its potential use in biotechnological processes. The lipase shows no fatty acid specificity in hydrolysis of coconut and soya bean oils. Short chain triglycerides were the preferred substrates in transesterification reactions. In both transesterification and hydrolysis of 1,3-dipalmytoyl-2-oleylglycerol the lipase shows selectivity for the 1,(3) position of triglycerides. The acetone powder catalysed the hydrolysis of triglycerides in 2,2,4- trimethylpentane (TMP) and was evaluated for use in the continuous production of poly-unsaturated fatty acids from soya bean oil in a packed bed reactor. Complete hydrolysis of 2.5% w v soya bean oil dissolved in TMP was achieved within 3 h of introduction of the oil solution and the hydrolysis decreased with time to between 60% and 80% depending on temperature conditions. The lipase activity found in the ungerminated seed and the characteristics that the lipase shows make Vernonia galamensis an attractive oilseed crop not only as an industrial oil source but also as a source of cheap lipase.

Insect acetyl-CoA carboxylase : activity during the larval, pupal and adult stages of insect development

1. The activity of the lipogenic enzyme, acetyl-CoA carboxylase, was investigated in four insect species; Bombyx mori (Lepidoptera), Tenebrio molitor (Coleoptera), Glossina morsitans and Sarcophaga nodosa (Diptera). 2. Acetyl-CoA carboxylase activity in larval, pupal and adult forms was compared with the saponifiable lipid mass at each stage of the life-cycle, and found to follow similar patterns except for Tenebrio molitor. 3. The results are examined in relation to known metabolic requirements for each insect.

Insect acetyl-CoA carboxylase: enzyme activity during adult development and after feeding in the tsetse fly, Glossina morsitans

Acetyl-CoA carboxylase (EC 6.1.4.2) activity in the adult tsetse fly (Glossina morsitans) increased 2-3 days after pupation to reach a plateau of between 0.4 and 0.6 mumol/min/mg after 7 days, and between 0.6 and 0.8 mumol/min/mg after 6 days in the abdomens of male and female flies, respectively. The enzyme showed a 50-70% increase in specific activity within 20 hr after a blood meal in previously starved flies. Lipogenesis and acetyl-CoA carboxylase activity were detected in the thorax, the abdominal cuticle and, in greatest quantity, in the fat body.