LAUSR

Abstract Background d -tagatose is regarded as one of the most valuable rare sugars in the current market and its biotechnological ways of production is a very hot topic as of today. As a ketohexose, d -tagatose having low-caloric value and 90% of sweetness with sucrose is a rare monosaccharide that exists extremely in low quantities in nature. Owing to distinct properties and beneficial functions on human health it has received a great interest and attained Generally Recognised as Safe (GRAS) status by the U.S. Food and Drug Administration (USFDA) in 2010. Scope and approach Due to scarcity in nature, production of d -tagatose either by chemical or biological methods is of utmost importance. In order to overcome the challenges that occur in chemical production, recently, biological process by using l -arabinose isomerase (L-AIs) for converting d -galactose to d -tagatose has allured researchers to find out more new ways to synthesize it in a cheap and eco-friendly manner. Herein, a brief summary on the scope of enzyme engineering methods like rational, semi-rational and directed evolution approaches to generate tailored L-AIs for improving d -tagatose yield and its function under harsh conditions are summarized. In addition, comparison of biochemical parameters and structural key aspects are also highlighted in this paper. Key findings and conclusions Till date, L-AIs from various microbial sources are identified and characterized. Elucidating crystal structures and catalytic mechanism has elevated the researcher's interest to modify the L-AIs at molecular level and demonstrate its potential that is suited for industrial settings. However, works to produce d -tagatose from cheap renewable feedstocks and methods like immobilization and cell-surface display of L-AIs for efficient uptake and biotransformation of d -galactose are scarcely reported. In future, by employing the aforementioned strategies, the research studies must be focused more on shaping L-AIs as powerful biocatalysts to produce d -tagatose at industrial scale that necessitates for the human welfare.