De Evans

Thermostability variation in alleles of barley beta-amylase

Abstract Thermostability assays in conjunction with IEF and molecular mapping were used to identify three beta-amylase alleles (Bmyl-Sd1, -Sd2L, -Sd2H) in cultivated barley and an additional allele (Bmy1-Sd3) in an accession of wild barley Hordeum vulgare ssp. spontaneum. The four forms of beta-amylase exhibit different rates of thermal inactivation in barley extracts. This variation was shown to persist after the proteolytic processing of the enzyme that occurs during germination. Three forms of beta-amylase representing the range of thermostabilities were purified and shown to have T50 temperatures of 56·8°C for the Sd2L enzyme, 58·5°C for the Sd1 enzyme, and 60·8°C for the Sd3 beta-amylase from wild barley. Analysis of the relationship between beta-amylase thermostability and fermentability, i.e. the yield of fermentable sugars obtained from starch hydrolysis during brewing in 42 commercial malt samples suggests that increased thermostability results in more efficient starch degradation. Screening for specific beta-amylase alleles is proposed as a method for increasing fermentability in malting barley.

Reasons for physically restraining patients and residents: a systematic review and content analysis

OBJECTIVE The purpose of this systematic review was to determine why people are physically restrained in the acute and residential care settings. METHOD A comprehensive search was undertaken of electronic databases to identify studies addressing the reasons for using physical restraint. Findings were synthesised using content analysis. RESULTS Twenty-three studies were identified. The most common reason for using restraints related to patient-oriented issues such as ensuring the safety of people. However, they are also commonly used to facilitate treatment, maintain the social environment and because of issues such as understaffing.

Assessing the impact of the level of diastatic power enzymes and their thermostability on the hydrolysis of starch during wort production to predict malt fermentability.

In this study, commercially produced malts were used for small-scale simulated mashing trials to investigate the impact of differences in the level and thermostability of malt diastatic power (DP) enzymes on the resultant wort fermentability. A modified European Brewery Convention/American Society Brewing Chemists mashing protocol was used with mash-in temperatures ranging between 45 and 76°C for full-malt and 30% rice adjunct mashes. Malt extract yield varied little with mashing temperature for most varieties in this temperature range. However, the fermentability, maltose content, and free amino nitrogen of that extract was considerably affected by mashing temperature with 65°C achieving the highest fermentability for all malt varieties. Multilinear regression analysis of full-malt and rice adjunct mashing trials at 65°C using 43 commercial malts showed that the level of α-amylase and total limit dextrinase activity, Kolbach Index, and the total β-amylase activity level and thermostability were the most important malt quality predictors of wort fermentability. These conclusions suggest that the conventional DP assessment could be replaced with the measurement of its component enzymes outlined above so that maltsters could better satisfy brewers malt quality expectations by blending and defining their malt quality in terms of these fermentability predicting factors. This information would be particularly useful to brewers who brew with multiple varieties and blends from different suppliers. The focus on individual enzyme characteristics by barley breeders is likely to provide selection targets that are more accurate and achievable.

Mutations of barley β-amylase that improve substrate-binding affinity and thermostability

Abstract. Three allelic forms of barley β-amylase (Sd1, Sd2H and Sd2L) exhibit different thermostability and kinetic properties. These differences critically influence the malting quality of barley varieties. To understand the molecular basis for the different properties of these three allelic forms, Sd1 and Sd2L β-amylase cDNAs were cloned, and the effects of the amino acid substitutions between them were evaluated by site-directed mutagenesis. The results showed that an R115C mutation is responsible for the difference in kinetic properties. This substitution resulted in an additional hydrogen bond which may create a more favourable environment for substrate-binding. The different thermostabilities of the β-amylase forms are due to two amino acid substitutions (V233A and L347S), which increased the enzymes thermostability index T50 by 1.9°C and 2.1°C, respectively. The increased thermostability associated with these two mutations may be due to relief of steric strain and the interaction of the protein surface with solvent water. Although both V233A and L347S mutations increased thermostability, they affected the thermostability in different ways. The replacement of L347 by serine seems to increase the thermostability by slowing thermal unfolding of the protein during heating, while the replacement of V233 by alanine appears to cause an acceleration of the refolding after heating. Because the different β-amylase properties determined by the three mutations (R115C, V233A and L347S) are associated with malting quality of barley variety, a mutant with high thermostability and substrate-binding affinity was generated by combining the three preferred amino acid residues C115, A233 and S347 together. A possible approach to producing barley varieties with better malting quality by genetic engineering is discussed.

The experience of physical restraint: a systematic review of qualitative research.

Abstract The objective of this review was to summarise the experience of physical restraint from the perspectives of the person subject to restraint and of their family. A review of interpretive and descriptive research was undertaken that entailed a comprehensive literature search. Studies were included in the review if they provided qualitative data on this experience. An interpretive data synthesis was undertaken to generate a composite description of the experience of restraint. Findings highlight the predominantly negative impact of physical restraint on the person restrained and their family. These findings support the most minimal use of restraint in health care and give voice to a relatively powerless and vulnerable group of people.

The properties and genetics of barley malt starch degrading enzymes

The properties and quality of barley malt starch degrading enzymes are of primary importance to the efficiency and profitability of brewing (beer and whiskey), and the bio-fuel (bio-ethanol) industries. The barley starch degrading enzymes hydrolyse starch into fermentable sugars that yeast converts into alcohol. This process is key for the alcohol producing industries as the starch substrate makes up approximately 60% of grain weight (Holtekjolen et al., 2006). Malted barley is the main source of the diastase or diastatic power (DP) enzymes that hydrolyse starch. The DP enzymes comprise the combined activity of α-amylase, β-amylase, α-glucosidase and limit dextrinase whose concerted action hydrolyse the α-(1,4) and a-(1,6) glucosyl linkages in starch (Fig. 6.1) into fermentable sugars (i.e., glucose, maltose, etc.), dextrins and limit dextrins. The actions of the DP enzymes are summarised as follows: (1) α-amylase cleaves α-(1,4)-linkages internally (endo-acting) to primarily produce oligosaccharides, limit dextrins and some fermentable sugars; (2) β-amylase cleaves α-(1,4)-linkages from the non-reducing ends (exo-acting) to produce maltose; (3) Limit dextrinase hydrolyses internal a-(1,6)-linkages (endo), to remove branch-points in amylopectin or α-limit dextrins; (4) α-Glucosidase primarily cleaves α-(1,4)-linkages from the non-reducing ends to produce glucose. Open image in new window Fig. 6.1 Schematic representation of starch hydrolysis

Beer foam: achieving a suitable head

The brand image of a beer is inexorably linked to the quality of the foam on that beer after dispense as a quality indicator that can be easily applied by all consumers. This is not surprising due to the visual appeal of the foam, its subtle role as a conduit for beer aromas and its contribution to the beer mouth feel. Similarly it is noted that consumers from different nations, regions or even genders have different preferences for the foam on their beer. This is divided by visual cues that include the foam stability, cling, strength, creaming, bubble size and whiteness. Thus Bamforth’s (1999) erstwhile boss who said “that generations of biochemists have done less for beer foam than the widget” is alienating a substantial portion of potential consumers from their beer brands because such foam does not meet their expectations. Foam quality is not just about “quick” fixes such as the inclusion of widgets, ever greater levels of tetra hop or gas composition but attention to the beer making process from grass to glass (malting variety breeding to dispense). Brewers do have solid options in manipulating the quality and quantity of malt foam positive proteins and selection of hop acids, the interaction of which provides the basis for foam stability and quality. Brewers also have a range of palliative options such as additives, gas composition, widgets and methods for dispense that can be used if suitable to the style of beer being produced. The main game is to use these options to optimise the foam quality of their brands and to consistently meet the expectations of the consumers that the brewer is targeting.

Don't be fobbed off, the substance of beer foam

A suitable head on a beer is one of the first characteristics by which consumers judge the quality of their beer; thus it is of vital importance to brewers. Beer foam quality is characterized by its stability, adherence to glass, and texture, which are inherently determined by the quality of the barley and hop raw materials used for beer production. In addition, beer production processes, addition of foam palliatives, packaging and method of dispense influence the basic foam quality determined by the raw materials. Elevated levels of key malt proteins and hop acids generally influence foam quality positively, while the inclusion of excessive levels of lipids, protein modification, and ethanol generally reduce foam quality. The primary objective of this review is to identify malt components that can be manipulated to produce beer foam of superior quality.

The systematic review report

Systematic reviews are increasingly being used in health care to support and guide clinical practice. However, the quality and relevance of the systematic review should be assessed before its findings are implemented into practice. To enable this appraisal, a comprehensive description of the review method and findings is required. This paper presents an overview of what information should be provided when systematic reviews are submitted for publication. The systematic review report should state the focus of the review and provide a description of the processes used during the search, critical appraisal, data abstraction and data synthesis phases of the review. The focus of the review is provided through the description of the review question and inclusion criteria. The search strategy must be fully reported and should include the specific databases searched, the search terms and the processes used. Information is also needed on how study quality was appraised and the processes used to summarise and synthesise the data. Complete reporting of the findings of the review is also required if the implications for practice are to be evaluated.

The fungal community structure of barley malts from diverse geographical regions correlates with malt quality parameters

Malt is a preferred base for fermentations that produce beer or whisky. Barley for malt is grown under diverse environments in different geographical locations. Malt provides an ecological niche for a varied range of microorganisms with both positive and negative effects on its quality for brewing. Little information exists in the literature on the microbial community structure of Australian malt as well as broader global geographical differences in the associated fungal and bacterial communities. The aims of the present study were to compare the bacterial and fungal community structures of Australian commercial malt with its international counterparts originating from different geographical regions using terminal restriction fragment length polymorphism (TRFLP) fingerprinting and clone library analyses of ribosomal RNA genes. Further, the relationship between malt associated microbial communities and conventional malt quality parameters was also compared. Results showed that differences in fungal communities of malts from different geographical location were more pronounced than bacterial communities. TRFLP analysis discriminated high quality commercial malts with low fungal loads from malts deliberately infected with fungal inocula (Fusarium/Penicillium). Malt moisture, beta-amylase, α-amylase and limit dextrinase contents showed significant correlations with fungal community structure. This investigation concluded that fungal community structure was more important to subsequent malt quality outcomes than bacteria.