title: Bioconversion of Glycerol to Dihydroxyacetone by immobilized Gluconacetobacter xylinus cells

authors: Black, Cathryn Sesengel

subjects: Glycerol

abstract: Dihydroxyacetone, (DHA) is one of the primary ingredients used in tanning products by the cosmetic industry. DHA reacts with the free amino acids on the epidermis to form a tan-like appearance. DHA is also a building block for lactic acid; that is, a common ingredient in the food industry. In the pharmaceutical industry, DHA is used as a precursor for 1, 2-propylene glycerol and methotrexate. 
Due to the Food and Drug Administration’s strict regulations, DHA is produced via microbial synthesis. This is because the chemical synthesis involves toxic chemical reactions with epichlorohydrin. This poses problems with a chemical widely used for human application. Currently, the industrial process of DHA is carried out under microbial synthesis of glycerol. The strain, Gluconobacter oxydans produces high DHA yields although its productivity is low. As a result, its high cost of production is reflected in its price.
Glycerol is the only organic compound that can be converted into DHA. The conversion requires oxidation of the secondary hydroxyl group by glycerol dehydrogenase (GlyDH). In this study, DHA was converted from glycerol using Gluconacetobacter xylinus (G.xylinus) in a large-scale reactor. Previously the strain, G.xylinus, has been shown to produce high DHA yields under immobilization. 
In this study, G.xylinus was immobilized inside two carrier materials- calcium alginate and chitosan-coated alginate beads. A series of investigations were carried out to determine the DHA conversion efficiency using the mentioned carriers. The conversion efficiency of alginate immobilized cells was investigated under varying initial glycerol concentrations of: 1%, 2%, 4% and 7% (w/v) and aeration rates of: 0.3, 0.6 and 1.0 vvm. This study found that the optimal glycerol concentration was at 2% (w/v) and the optimal aeration rate was at 0.3 vvm. The DHA conversion efficiency of chitosan-alginate immobilized cells was also tested under the same aeration rate previously mentioned. The investigation found that chitosan coating provided greater stability to the alginate matrix with increased aeration rate. The optimal aeration rate was found at 1.0 vvm.

text: Bioconversion of Glycerol to Dihydroxyacetone by immobilized Gluconacetobacter xylinus cells Dihydroxyacetone, (DHA) is one of the primary ingredients used in tanning products by the cosmetic industry. DHA reacts with the free amino acids on the epidermis to form a tan-like appearance. DHA is also a building block for lactic acid; that is, a common ingredient in the food industry. In the pharmaceutical industry, DHA is used as a precursor for 1, 2-propylene glycerol and methotrexate. 
Due to the Food and Drug Administration’s strict regulations, DHA is produced via microbial synthesis. This is because the chemical synthesis involves toxic chemical reactions with epichlorohydrin. This poses problems with a chemical widely used for human application. Currently, the industrial process of DHA is carried out under microbial synthesis of glycerol. The strain, Gluconobacter oxydans produces high DHA yields although its productivity is low. As a result, its high cost of production is reflected in its price.
Glycerol is the only organic compound that can be converted into DHA. The conversion requires oxidation of the secondary hydroxyl group by glycerol dehydrogenase (GlyDH). In this study, DHA was converted from glycerol using Gluconacetobacter xylinus (G.xylinus) in a large-scale reactor. Previously the strain, G.xylinus, has been shown to produce high DHA yields under immobilization. 
In this study, G.xylinus was immobilized inside two carrier materials- calcium alginate and chitosan-coated alginate beads. A series of investigations were carried out to determine the DHA conversion efficiency using the mentioned carriers. The conversion efficiency of alginate immobilized cells was investigated under varying initial glycerol concentrations of: 1%, 2%, 4% and 7% (w/v) and aeration rates of: 0.3, 0.6 and 1.0 vvm. This study found that the optimal glycerol concentration was at 2% (w/v) and the optimal aeration rate was at 0.3 vvm. The DHA conversion efficiency of chitosan-alginate immobilized cells was also tested under the same aeration rate previously mentioned. The investigation found that chitosan coating provided greater stability to the alginate matrix with increased aeration rate. The optimal aeration rate was found at 1.0 vvm.

year: 2013

title: Why does NZ’s new energy plan sideline renewables and ignore progress made already?

authors: Barton, Barry

subjects: electricity

abstract: With the public concerned about energy prices and security of supply, the government’s recently released energy package naturally attracted a lot of attention.

The package was criticised for being unlikely to either bring down prices or increase construction for new generation. But it’s just as important we see how much the plan assumes fossil fuels are the only answer, and how little it connects with important reforms already underway.

text: Why does NZ’s new energy plan sideline renewables and ignore progress made already? With the public concerned about energy prices and security of supply, the government’s recently released energy package naturally attracted a lot of attention.

The package was criticised for being unlikely to either bring down prices or increase construction for new generation. But it’s just as important we see how much the plan assumes fossil fuels are the only answer, and how little it connects with important reforms already underway.

year: 2025

title: Racism and Employment: A Narrative Review of Aotearoa New Zealand and International Qualitative Studies

authors: Tan, Kyle K. H.

abstract: In Aotearoa New Zealand, employment inequities exist for minoritised ethnic groups (Māori, Pasifika, Asian, racialised migrants and refugees) in the forms of barriers to employment, occupation inequities, differences in promotion to leadership roles, ethnic pay gaps and discriminatory experiences at workplaces. In this review, we compiled Aotearoa qualitative studies to depict the dynamics of racism alongside other intersectional forms of prejudices that disadvantage the employment processes and career progression of minoritised ethnicities. Literature gaps in Aotearoa research were identified through reviewing international literature published between 2016 and 2021. Reviewed Aotearoa studies were categorised into three themes: unemployment and underemployment, workplace discrimination, and strategies for navigating racism. Drawing upon a framework that recognises racialised processes as spanning across micro- (individual), meso- (organisational) and macro- (institutional) levels, we found most Aotearoa studies analysing racism in the workplace focus on micro-level experiences. Compared with international literature, research in Aotearoa has yet to consider the roles of organisations and technologies as racialised structures that engender employment inequities, and the interaction of individuals in response to meso- and macro-structures that build on settler colonialism and racism. Our review echoes the call of Aotearoa scholars to name racism as the overarching oppressive mechanism embedded within organisations and to use anti-racism praxes such as te Tiriti o Waitangi as a way forward to promote employment equity.

text: Racism and Employment: A Narrative Review of Aotearoa New Zealand and International Qualitative Studies In Aotearoa New Zealand, employment inequities exist for minoritised ethnic groups (Māori, Pasifika, Asian, racialised migrants and refugees) in the forms of barriers to employment, occupation inequities, differences in promotion to leadership roles, ethnic pay gaps and discriminatory experiences at workplaces. In this review, we compiled Aotearoa qualitative studies to depict the dynamics of racism alongside other intersectional forms of prejudices that disadvantage the employment processes and career progression of minoritised ethnicities. Literature gaps in Aotearoa research were identified through reviewing international literature published between 2016 and 2021. Reviewed Aotearoa studies were categorised into three themes: unemployment and underemployment, workplace discrimination, and strategies for navigating racism. Drawing upon a framework that recognises racialised processes as spanning across micro- (individual), meso- (organisational) and macro- (institutional) levels, we found most Aotearoa studies analysing racism in the workplace focus on micro-level experiences. Compared with international literature, research in Aotearoa has yet to consider the roles of organisations and technologies as racialised structures that engender employment inequities, and the interaction of individuals in response to meso- and macro-structures that build on settler colonialism and racism. Our review echoes the call of Aotearoa scholars to name racism as the overarching oppressive mechanism embedded within organisations and to use anti-racism praxes such as te Tiriti o Waitangi as a way forward to promote employment equity.

year: 2024-01-01