Bio-Based Polyisoprene Can Mitigate Climate Change and Deforestation in Expanding Rubber Production

Biomass is a promising renewable feedstock to produce polyisoprene for the rubber industry. Through metabolic engineering, sugars derived from pretreated and hydrolyzed cellulose and hemicellulose can be directly fermented to isoprene to produce rubber. Here we investigate the life cycle environmental impact of isoprene fermentation to produce bio-polyisoprene from agricultural residues (of Zea mays L.). Results show that the greenhouse gas (GHG) intensity of bio-polyisoprene (−4.59 kg CO2e kg−1) is significantly lower than that of natural rubber (Hevea brasiliensis) and synthetic rubber (−0.79 and 2.41 kg CO2e kg−1, respectively), while supporting a circular biogenic carbon economy. We found the land use intensity of bio-polyisoprene to be 0.25 ha metric ton−1, which is 84% lower than that from rubber tree plantations. We compare the direct fermentation to isoprene results with indirect fermentation to isoprene through the intermediate, methyl butyl ether, where dehydration to isoprene is required. The direct fermentation of isoprene reduces reaction steps and unit operations, an expected outcome when employing process intensification, but our results show additional energy conservation and reduced contribution to climate change. Among the ReCiPe life cycle environmental impact metrics evaluated, air emission related impacts are high for bio-polyisoprene compared to those for natural and synthetic rubber. Those impacts can be reduced with air emission controls during production. All other metrics showed an improvement for bio-polyisoprene compared to natural and synthetic rubber.

Two Step and Direct Fermentation in the Production of Ethanol from Starch: A Short Review

Ethanol as a renewable fuel has been widely produced in various countries. One source of raw material for producing ethanol is starch. The process of producing ethanol from starch needs to be pretreated so that starch molecules can split into smaller ones. However, this process requires pre-treatment which will expensive more than ethanol from sugar. There are two types of pretreatment i.e. two-step ethanol production and direct fermentation. There is two kind of hydrolysis, acid hydrolysis, and enzymatic hydrolysis. Two-step ethanol production is a conventional method that separates pretreatment and fermentation process, while direct fermentation is the direct production of starch into ethanol using recombinant yeast that co-produces enzymes such as amylose and glucoamylase. Two-step ethanol production has the advantage of high yield but needs high cost whereas, direct fermentation has the advantage of low-cost production but needs longer time. Common starch to ethanol production consists of two stages, namely hydrolysis of raw materials into glucose and fermentation into ethanol. Both of these processes can be run on average at temperatures of 30-80^oC with a pH range of 4-6 and varying time intervals. The enzyme used depends on the source of the starch, but the most commonly used is <em>Saccharomyces cerevisiae</em>.

Influence of consortia of lactic acid microorganisms on the dynamics of active and titratable acidity at the main stage of fermentation of white cabbage

Fermented cabbage is traditionally produced naturally, where under the action of lactic acid bacteria contained in raw materials, carbohydrates are converted into lactic acid. However, the direct fermentation process does not always lead to an optimal quality product. That is why the use of lactic acid microorganisms is a good alternative to the direct fermentation of cabbage, as with the help of starter cultures the process can be controlled. In this connection, the use of strains of lactic acid microorganisms allows to achieve rapid production of lactic and acetic acids and leads to a rapid decrease in pH, which in turn leads to the suppression of pathogenic microflora, and therefore to the creation of favorable conditions for the fermentation process. The aim of this study was to study the effect of consortia of lactic acid microorganisms on the dynamics of active and titratable acidity in the main stage of fermentation of white cabbage of the variety "Parus". For the study, the prepared modified model medium (MMC) from cabbage was used. In this work, we used lactic acid bacteria Leuconostoc mesenteroides and its consortia: L. mesenteroides + L. casei, L. mesenteroides + L. plantarum, L. mesenteroides + L. brevis, L. mesenteroides + L. casei + L. plantarum, L. mesenteroides + L. plantarum + L. brevis, L. mesenteroides + L. brevis + L. casei. Mathematical processing was carried out according to the obtained experimental data. Analysis of experimental data showed that at the main stage of fermentation the relationship of lactic acid microorganisms in the studied consortia was expressed by synergistic and antagonistic properties. In this case, the best results on the dynamics of growth of active and titratable acidity were obtained in consortiums L. mesenteroides + L. plantarum, L. mesenteroides + L. casei + L. plantarum, L. mesenteroides + L. plantarum + L. brevis.