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ABSTRACT Research in geocryology is currently principally concerned with the effects of climate change on permafrost terrain. The motivations for most of the research are (1) quantification of the anticipated net emissions of CO₂and CH₄from warming and thaw of near‐surface permafrost and (2) mitigation of effects on infrastructure of such warming and thaw. Some of the effects, such as increases in ground temperature or active‐layer thickness, have been observed for several decades. Landforms that are sensitive to creep deformation are moving more quickly as a result, andRock Glacier Velocityis now part of the Essential Climate VariablePermafrostof the Global Climate Observing System. Other effects, for example, the occurrence of physical disturbances associated with thawing permafrost, particularly the development of thaw slumps, have noticeably increased since 2010. Still, others, such as erosion of sedimentary permafrost coasts, have accelerated. Geochemical effects in groundwater from trace elements, including contaminants, and those that issue from the release of sediment particles during mass wasting have become evident since 2020. Net release of CO₂and CH₄from thawing permafrost is anticipated within two decades and, worldwide, may reach emissions that are equivalent to a large industrial economy. The most immediate local concerns are for waste disposal pits that were constructed on the premise that permafrost would be an effective and permanent containment medium. This assumption is no longer valid at many contaminated sites. The role of ground ice in conditioning responses to changes in the thermal or hydrological regimes of permafrost has re‐emphasized the importance of regional conditions, particularly landscape history, when applying research results to practical problems. 

Abstract Efficient co‐utilization of mixed sugar feedstocks remains a biomanufacturing challenge, thus motivating ongoing efforts to engineer microbes for improved conversion of glucose−xylose mixtures. This study focuses on enhancing phenylalanine production by engineeringEscherichia colito efficiently co‐utilize glucose and xylose. Flux balance analysis identified E4P flux as a bottleneck which could be alleviated by increasing the xylose‐to‐glucose flux ratio. A mutant copy of the xylose‐specific activator (XylR) was then introduced into the phenylalanine‐overproducingE. coliNST74, which relieved carbon catabolite repression and enabled efficient glucose−xylose co‐utilization. Carbon contribution analysis through¹³C‐fingerprinting showed a higher preference for xylose in the engineered strain (NST74X), suggesting superior catabolism of xylose relative to glucose. As a result, NST74X produced 1.76 g/L phenylalanine from a model glucose−xylose mixture; a threefold increase over NST74. Then, using biomass‐derived sugars, NST74X produced 1.2 g/L phenylalanine, representing a 1.9‐fold increase over NST74. Notably, and consistent with the carbon contribution analysis, thexylR*mutation resulted in a fourfold greater maximum rate of xylose consumption without significantly impeding the maximum rate of total sugar consumption (0.87 vs. 0.70 g/L‐h). This study presents a novel strategy for enhancing phenylalanine production through the co‐utilization of glucose and xylose in aerobicE. colicultures, and highlights the potential synergistic benefits associated with using substrate mixtures over single substrates when targeting specific products.