Bioethanol has been identified as the mostly used biofuel worldwide since it significantly contributes to the reduction of crude oil consumption and environmental pollution. It can be produced from various types of feedstocks such as sucrose, starch, lignocellulosic and algal biomass through fermentation process by microorganisms. Compared to other types of microoganisms, yeasts especially Saccharomyces cerevisiae is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars. However, there are some challenges in yeast fermentation which inhibit ethanol production such as high temperature, high ethanol concentration and the ability to ferment pentose sugars. Various types of yeast strains have been used in fermentation for ethanol production including hybrid, recombinant and wild-type yeasts. Yeasts can directly ferment simple sugars into ethanol while other type of feedstocks must be converted to fermentable sugars before it can be fermented to ethanol. The common processes involves in ethanol production are pretreatment, hydrolysis and fermentation. Production of bioethanol during fermentation depends on several factors such as temperature, sugar concentration, pH, fermentation time, agitation rate, and inoculum size. The efficiency and productivity of ethanol can be enhanced by immobilizing the yeast cells. This review highlights the different types of yeast strains, fermentation process, factors affecting bioethanol production and immobilization of yeasts for better bioethanol production.

No abstract

Stingless bees harbor lactic acid bacteria (LAB) which possesses multiple beneficial properties. However, there is no report on LAB in stingless bee from Sabah and their products. This study aimed to isolate LAB from several stingless bee species and their products as well as to perform characterization and safety assessments. A total of 104 strains were isolated and seven potential antimicrobial LAB isolates were identified from stingless bee and their products. Characterization, identification, and assessments were performed on seven (A2b, B3b, P1b, H4b, A6, B5, and B10) LAB that exert potential antimicrobial activity against Listeria monocytogenes ATCC 7644. The A6 isolate was closely related to the Lactobacillus pentosus species whereas isolates B5 and B10 were closely related to Weissella paramesenteroides species. Finally, isolates P1b, H4b, B3b, and A2b were closely related to the Enterococcus sp. These seven LAB isolates were able to survive in stimulated gastrointestinal tract conditions (acidic, salt, bile salt, and temperature). The carbon fermentation, proteolytic activities, acidification, milk coagulation, and wide antibiotic susceptibility testing of seven LAB isolates revealed their potential used as a probiotic and fermentation purposes. Therefore, more studies are warranted to investigate the potential of these LAB isolates towards applications in probiotic and fermentation.

-

No abstract