The state of green technologies in South Africa

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Robust yeast for the production of bioethanol from steam-exploded sugarcane bagasse

Robust yeast with high inhibitor, temperature and osmotic tolerance remain a critical requirement for the sustainable production of lignocellulosic bioethanol. In this work, grape marc was selected as extreme environment to search for innately robust yeast because of its limited nutrients, exposure to solar radiation, temperature fluctuations and ethanol content. Forty newly isolated Saccharomyces cerevisiae strains gave high ethanol yields at 40 \ub0C when inoculated in minimal media at high sugar concentrations. Moreover, the isolates showed distinct inhibitor-tolerance in defined broth supplemented with increasing levels of single inhibitors or a cocktail of inhibitory compounds. Both fermentative abilities and inhibitor resistance were greater than those exhibited by industrial and commercial S. cerevisiae benchmark yeast. The isolate Fm17, exhibiting the most promising phenotype, was then evaluated to ferment liquor from steam-exploded sugarcane bagasse, having high concentrations of weak acids, furans and aldehydes. The selected strain produced high alcohol levels with an ethanol yield equal to 89% of the theoretical. This work demonstrated that yeast with high multiple stress tolerance can be obtained from unconventional ecological niches, such as grape marc. The selected yeast represents a promising platform to develop robust engineered strains suitable for the one-step processing of biomass into ethanol

Developing novel yeast strains for the consolidated bioprocessing of starchy substrates into bioethanol

Bioethanol belongs to the large family of renewable fuels that can be used as alternatives to fossil oil, with hundreds of billions of liters produced in the US and Brazil from maize and sugarcane. However, criticism due to the rise of food prices and food shortage is impeding the global implementation of bioethanol production from crops. Second-generation bioethanol could be made from non-food feedstocks rich in starch and lignocellulose, consisting of food waste or processing residues. The conventional first-generation bioethanol production from starch is a well-established technology, based on a multiple-step process that is hardly sustainable: high energy demand is firstly required to pretreat the material at high temperatures, then expensive commercial enzymes are needed to breakdown the granules in order to obtain free glucose for the final fermentation step. In this scenario, large cost reductions can be achieved through process integration (consolidated bioprocessing, CBP) by using a new amylolytic and fermenting microbe able to directly convert starchy biomass into fuel in a single bioreactor. To date, no natural CBP microorganism has been described. Saccharomyces cerevisiae is the most common fermenting yeast, traditionally used in the food industry. The high fermenting activity, the Generally Regarded As Safe (GRAS) status and industrial robustness are desirable characteristics for large scale bioethanol production. Unfortunately, S. cerevisiae lacks hydrolytic enzymes and cannot use starch as a carbon source. A new S. cerevisiae strain genetically engineered with fungal amylases can significantly contribute to improve the feasibility of granular starch hydrolysis. This study aimed at searching for novel yeast strains with high fermenting abilities on starchy by-products to be used as host strains for the development of new and efficient CBP yeast. A cluster of twenty-one novel S. cerevisiae isolates was screened for their fermenting potential and the industrial Ethanol RedTM was used as the benchmark. The fermenting performances were assessed on starchy substrates, broken rice, and raw corn starch, at high loading (20% w/v) in simultaneous saccharification and fermentation (SSF) set up at 30\ub0 C. The starch hydrolysis was carried out with the commercial amylases cocktail STARGENTM 002. The novel S. cerevisiae L20 strain outperformed the industrial benchmark and was selected as the host strain for the development of novel starch-to-ethanol CBP strains through the engineering of two efficient starch-hydrolyzing genes from Aspergillus tubigensis: the alpha-amylase AmyA and the glucoamylase GlaA. To this aim, both \uf064-integration and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technologies are being currently applied. The transformants strains obtained so far have been assessed for enzymatic activity, resulting in excellent performances, and will be further employed for fermentation of starchy substrates

Research and Measuring Technology Needs to Better Model and Measure Fatigue Crack Development of Thinly Surfaced Asphalt Road Pavements

The root cause of premature failures in relatively thin (<50 mm) asphalt surfaced roads is often a challenge to solve during forensic investigations in South Africa (SA). This description is based on peer review type discussions with forensic investigations experts as well as published research papers. The areas of ignorance or areas where research effort is needed are identified. These observations serve to identify areas of new knowledge needed in terms of actual verification with measurements, measurement technology, and modeling of the observed phenomena. The main objectives of this discussion paper are to highlight the evolution of distress development in asphalt layers starting from the identification and description of the kind of microcracks, effects of microcracks in the debonding of the asphalt layer from lower layer, and vehicle–pavement interactions (VPI) of moving truck wheels focusing on the thin asphalt layer. Specific reference is made to the need to measure and model the effects of bow waves in front of and next to the loaded rolling wheel

Research and Measuring Technology Needs to Better Model and Measure Fatigue Crack Development of Thinly Surfaced Asphalt Road Pavements

The root cause of premature failures in relatively thin (<50 mm) asphalt surfaced roads is often a challenge to solve during forensic investigations in South Africa (SA). This description is based on peer review type discussions with forensic investigations experts as well as published research papers. The areas of ignorance or areas where research effort is needed are identified. These observations serve to identify areas of new knowledge needed in terms of actual verification with measurements, measurement technology, and modeling of the observed phenomena. The main objectives of this discussion paper are to highlight the evolution of distress development in asphalt layers starting from the identification and description of the kind of microcracks, effects of microcracks in the debonding of the asphalt layer from lower layer, and vehicle–pavement interactions (VPI) of moving truck wheels focusing on the thin asphalt layer. Specific reference is made to the need to measure and model the effects of bow waves in front of and next to the loaded rolling wheel

Fruit waste streams in South Africa and their potential role in developing a bio-economy

Current and previous studies on bio-based (fruit) wastes and wastewaters, with a particular emphasis on research in South Africa, were reviewed. Previous studies have focused predominantly on the beneficiation and application of fruit waste as a feedstock for renewable energy. A definite gap in knowledge and application of fruit waste streams with regard to enzyme production as a value-added product is identified. The characteristics and composition of each type of fruit waste are highlighted and their potential as feedstocks in the production of value-added products is identified. The conversion of agri-industrial wastewaters to bioenergy and value-added products is discussed, with special mention of the newly published South African Bio-Economy Strategy, and the potential production of biofuels and enzymes from waste streams using recombinant Aspergillus strains. Finally, to maximise utilisation of waste streams in South Africa and abroad, a conceptual model for an integrated system using different technologies is proposed