Starch is an essential factor affecting the quality of flue-cured tobacco, and high starch content can affect the sensory quality and safety. Recently, the degradation of macromolecules in tobacco raw materials by using additional microorganisms to improve their intrinsic quality and safety has become a new research hotspot in the tobacco industry. However, the technical maturity and application scale are limited. Our study analyzed the correlation between microbial community composition and volatile components on the surface of tobacco leaves from 14 different grades in Fujian tobacco-producing areas. The PICRUSt software was utilized to predict the function of the microbial community present in tobacco leaves. Furthermore, dominant strains that produced amylase were screened out, and an enzyme solution was prepared to enhance the flue-cured tobacco flavor. Changes in the content of macromolecules and volatile components were determined, and sensory evaluations were conducted to assess the overall quality of the tobacco leaves. The results showed that the dominant bacterial genera on the surface of Fujian tobacco leaves were Variovorax, Sphingomonas, Bacillus, etc. Bacillus was positively correlated with various volatile components, which contributed to the sweet and aromatic flavors of Fujian flue-cured tobacco. The main genetic functions of Fujian flue-cured tobacco surface bacteria were carbohydrate metabolism and amino acid metabolism. After treating flue-cured tobacco with an enzyme preparation prepared by the fermentation of Paenibacillus amylolyticus A17 #, the content of starch, pectin, and cellulose in flue-cured tobacco decreased significantly compared with the control group. Meanwhile, the content of total soluble sugar and reducing sugar was significantly increased, and the volatile aroma components, such as 3-hydroxy--damascone, 2,3-dihydro-3,5-dihydroxy-6-methyl-4 H-Pyran-4-one, ethyl palmitate, ethyl linolenic acid, etc., were significantly increased. The aroma quality and quantity of flue-cured tobacco were enhanced, while impurities were reduced. The smoke characteristics were improved, with increased fineness, concentration, and moderate strength. The taste characteristics were also improved, with reduced irritation and a better aftertaste. In conclusion, Bacillus, as the dominant genus in the abundance of bacterial communities on tobacco surfaces in Fujian, had an essential impact on the flavor of tobacco leaves by participating in carbohydrate metabolism and finally forming the unique flavor style of flue-cured tobacco in Fujian tobacco-producing areas. Paenibacillus amylolyticus A17 #, a target strain with amylase-producing ability, was screened from the surface of Fujian flue-cured tobacco. The enzyme preparation, produced by the fermentation of Paenibacillus amylolyticus A17 #, was utilized to reduce the content of macromolecules, increase the content of water-soluble total sugar and reducing sugar, and produce a variety of crucial volatile aroma components, which had a significant improvement on the quality of tobacco leaves.

Lignin is one of the most widespread organic compounds found on earth, boasting a wealth of aromatic molecules. The use of lignin feedstock for biochemical productions is of great importance for achieving “carbon neutrality.” In recent years, a strategy for lignin valorization known as the “bio-funnel” has been proposed as a means to generate a variety of commercially valuable chemicals from lignin-derived compounds. The implementation of biocatalysis and metabolic engineering techniques has substantially advanced the biotransformation of depolymerized lignin into chemicals and materials within the supply chain. In this review, we present an overview of the latest advancements in microbial upcycling of depolymerized lignin into value-added chemicals. Besides, the review provides insights into the problems facing current biological lignin valorization while proposing further research directions to improve these technologies for the extensive accomplishment of the lignin upcycling.

Amylase is a biological macromolecule that catalyzes the hydrolysis of starch or glycogen. It has a wide range of applications in various fields such as sugar making, pulp making, textiles, and medicine. There are different types of amylases, with α-amylase and β-amylase being the most common. Additionally, the structures and catalytic properties of amylases produced by different species vary. This article reviews the purification, enzymatic properties, and structural characterization of amylase, providing a reference for clarifying the catalytic characteristics of amylase and better controlling its catalytic reaction.